Showing papers by "Fred Hutchinson Cancer Research Center published in 1998"
TL;DR: The data suggest that two global mechanisms of gene regulation, DNA methylation and histone deacetylation, can be linked by MeCP2, an abundant nuclear protein that is essential for mouse embryogenesis.
Abstract: Cytosine residues in the sequence 5'CpG (cytosine-guanine) are often postsynthetically methylated in animal genomes. CpG methylation is involved in long-term silencing of certain genes during mammalian development and in repression of viral genomes. The methyl-CpG-binding proteins MeCP1 and MeCP2 interact specifically with methylated DNA and mediate transcriptional repression. Here we study the mechanism of repression by MeCP2, an abundant nuclear protein that is essential for mouse embryogenesis. MeCP2 binds tightly to chromosomes in a methylation-dependent manner. It contains a transcriptional-repression domain (TRD) that can function at a distance in vitro and in vivo. We show that a region of MeCP2 that localizes with the TRD associates with a corepressor complex containing the transcriptional repressor mSin3A and histone deacetylases. Transcriptional repression in vivo is relieved by the deacetylase inhibitor trichostatin A, indicating that deacetylation of histones (and/or of other proteins) is an essential component of this repression mechanism. The data suggest that two global mechanisms of gene regulation, DNA methylation and histone deacetylation, can be linked by MeCP2.
3,396 citations
TL;DR: The rationale for the interventions being studied in each of the CT components and for the inclusion of the OS component is described, including a brief description of the scientific and logistic complexity of the WHI.
2,310 citations
TL;DR: This review summarizes the factors that contribute to antifungal drug resistance on three levels: clinical factors that result in the inability to successfully treat refractory disease; cellular factors associated with a resistant fungal strain; and molecular factors that are ultimately responsible for the resistance phenotype in the cell.
Abstract: In the past decade, the frequency of diagnosed fungal infections has risen sharply due to several factors, including the increase in the number of immunosuppressed patients resulting from the AIDS epidemic and treatments during and after organ and bone marrow transplants. Linked with the increase in fungal infections is a recent increase in the frequency with which these infections are recalcitrant to standard antifungal therapy. This review summarizes the factors that contribute to antifungal drug resistance on three levels: (i) clinical factors that result in the inability to successfully treat refractory disease; (ii) cellular factors associated with a resistant fungal strain; and (iii) molecular factors that are ultimately responsible for the resistance phenotype in the cell. Many of the clinical factors that contribute to resistance are associated with the immune status of the patient, with the pharmacology of the drugs, or with the degree or type of fungal infection present. At a cellular level, antifungal drug resistance can be the result of replacement of a susceptible strain with a more resistant strain or species or the alteration of an endogenous strain (by mutation or gene expression) to a resistant phenotype. The molecular mechanisms of resistance that have been identified to date in Candida albicans include overexpression of two types of efflux pumps, overexpression or mutation of the target enzyme, and alteration of other enzymes in the same biosynthetic pathway as the target enzyme. Since the study of antifungal drug resistance is relatively new, other factors that may also contribute to resistance are discussed.
1,321 citations
TL;DR: It is found that neither addition of hTERT nor induction of telomerase activity by E6, both of which are active in maintaining telomere length, results in immortalization, and inactivation of the Rb/p16 pathway by E7 or downregulation of p16 expression, in combination with telomersase activity, is able to immortalize epithelial cells efficiently.
Abstract: Normal human cells undergo a limited number of divisions in culture and enter a non-dividing state called replicative senescence Senescence is accompanied by several changes, including an increase in inhibitors of cyclin-dependent kinases and telomere shortening The mechanisms by which viral oncogenes reverse these processes are not fully understood, although a general requirement for oncoproteins such as human papillomavirus E6 and E7 has suggested that the p53 and Rb pathways are targeted Expression of the catalytic component of telomerase, hTERT, alone significantly extends the lifespan of human fibroblasts Here we show that telomerase activity is not sufficient for immortalization of human keratinocyte or mammary epithelial cells: we find that neither addition of hTERT nor induction of telomerase activity by E6, both of which are active in maintaining telomere length, results in immortalization Inactivation of the Rb/p16 pathway by E7 or downregulation of p16 expression, in combination with telomerase activity, however, is able to immortalize epithelial cells efficiently Elimination of p53 and of the DNA-damage-induced G1 checkpoint is not necessary for immortalization, neither is elimination of p19ARF
1,248 citations
Book•
[...]
01 Jan 1998
TL;DR: For example, it has become increasingly clear over the past two decades that knowledge from one organism, even one so simple as a worm, can provide tremendous power when connected with knowledge from other organisms.
Abstract: Why should one study a worm? This simple creature is one of several “model” organisms that together have provided tremendous insight into how all organisms are put together. It has become increasingly clear over the past two decades that knowledge from one organism, even one so simple as a worm, can provide tremendous power when connected with knowledge from other organisms. And because of the experimental accessibility of nematodes, knowledge about worms can come more quickly and cheaply than knowledge about higher organisms.
1,138 citations
TL;DR: In this paper, the expression and recognition of a major histocompatibility complex (MHC) class I-related molecule, MICA, matches this localization, and the closely related MICB were recognized by intestinal epithelial T cells expressing diverse Vδ1 γδ TCRs.
Abstract: T cells with variable region Vδ1 γδ T cell receptors (TCRs) are distributed throughout the human intestinal epithelium and may function as sentinels that respond to self antigens. The expression of a major histocompatibility complex (MHC) class I–related molecule, MICA, matches this localization. MICA and the closely related MICB were recognized by intestinal epithelial T cells expressing diverse Vδ1 γδ TCRs. These interactions involved the α1α2 domains of MICA and MICB but were independent of antigen processing. With intestinal epithelial cell lines, the expression and recognition of MICA and MICB could be stress-induced. Thus, these molecules may broadly regulate protective responses by the Vδ1 γδ T cells in the epithelium of the intestinal tract.
1,080 citations
TL;DR: Examination of HLA-E antigen distribution indicated that it is detectable on the surface of a wide variety of cell types, consistent with the prediction that the ligand for CD94/NKG2A is expressed ubiquitously.
Abstract: We previously showed that the availability of a nonamer peptide derived from certain HLA class I signal sequences is a necessary requirement for the stabilization of endogenous HLA-E expression on the surface of 721.221 cells. This led us to examine the ability of HLA-E to protect HLA class I transfectants from natural killer (NK) cell-mediated lysis. It was possible to implicate the CD94/NKG2A complex as an inhibitory receptor recognizing this class Ib molecule by using as target a .221 transfectant selectively expressing surface HLA-E. HLA-E had no apparent inhibitory effect mediated through the identified Ig superfamily (Ig-SF) human killer cell inhibitory receptors or ILT2/LIR1. Further studies of CD94/NKG2+ NK cell-mediated recognition of .221 cells transfected with different HLA class I allotypes (i.e., -Cw4, -Cw3, -B7) confirmed that the inhibitory interaction was mediated by CD94/NKG2A recognizing the surface HLA-E molecule, because only antibodies directed against either HLA-E, CD94, or CD94/NKG2A specifically restored lysis. Surface stabilization of HLA-E in cold-treated .221 cells loaded with appropriate peptides was sufficient to confer protection, resulting from recognition of the HLA class Ib molecule by the CD94/NKG2A inhibitory receptor. Consistent with the prediction that the ligand for CD94/NKG2A is expressed ubiquitously, our examination of HLA-E antigen distribution indicated that it is detectable on the surface of a wide variety of cell types.
944 citations
TL;DR: Alcohol consumption is associated with a linear increase in breast cancer incidence in women over the range of consumption reported by most women, and reducing alcohol consumption is a potential means to reduce breast cancer risk.
Abstract: Objective. - To assess the risk of invasive breast cancer associated with total and beverage-specific alcohol consumption and to evaluate whether dietary and nondietary factors modify the association. Data Sources. - We included in these analyses 6 prospective studies that had at least 200 incident breast cancer cases, assessed long-term intake of food and nutrients, and used a validated diet assessment instrument. The studies were conducted in Canada, the Netherlands, Sweden, and the United States. Alcohol intake was estimated by food frequency questionnaires in each study. The studies included a total of 322 647 women evaluated for up to 11 years, including 4335 participants with a diagnosis of incident invasive breast cancer. Data Extraction. - Pooled analysis of primary data using analyses consistent with each study's original design and the random-effects model for the overall pooled analyses. Data Synthesis. - For alcohol intakes less than 60 g/d (reported by >99% of participants), risk increased linearly with increasing intake; the pooled multivariate relative risk for an increment of 10 g/d of alcohol (about 0.75-1 drink) was 1.09 (95% confidence interval [CI], 1.04-1.13; P for heterogeneity among studies, .71). The multivariate- adjusted relative risk for total alcohol intakes of 30 to less than 60 g/d (about 2-5 drinks) vs nondrinkers was 1.41 (95% CI, 1.18-1.69). Limited data suggested that alcohol intakes of at least 60 g/d were not associated with further increased risk. The specific type of alcoholic beverage did not strongly influence risk estimates. The association between alcohol intake and breast cancer was not modified by other factors. Conclusions. - Alcohol consumption is associated with a linear increase in breast cancer incidence in women over the range of consumption reported by most women. Among women who consume alcohol regularly, reducing alcohol consumption is a potential means to reduce breast cancer risk.
892 citations
TL;DR: A new primer design strategy for PCR amplification of unknown targets that are related to multiply-aligned protein sequences that consists of a short 3' degenerate core region and a longer 5' consensus clamp region, which demonstrates the practical utility of this hybrid primer method.
Abstract: We describe a new primer design strategy for PCR amplification of unknown targets that are related to multiply-aligned protein sequences. Each primer consists of a short 34 degenerate core region and a longer 54 consensus clamp region. Only 3‐4 highly conserved amino acid residues are necessary for design of the core, which is stabilized by the clamp during annealing to template molecules. During later rounds of amplification, the non-degenerate clamp permits stable annealing to product molecules. We demonstrate the practical utility of this hybrid primer method by detection of diverse reverse transcriptaselike genes in a human genome, and by detection of C 5 DNA methyltransferase homologs in various plant DNAs. In each case, amplified products were sufficiently pure to be cloned without gel fractionation. This COnsensus-DEgenerate Hybrid Oligonucleotide Primer (CODEHOP) strategy has been implemented as a computer program that is accessible over the World Wide Web (http://blocks.fhcrc.org/codehop.html ) and is directly linked from the BlockMaker multiple sequence alignment site for hybrid primer prediction beginning with a set of related protein sequences.
809 citations
TL;DR: It is shown that both p27 nullizygous and p27 heterozygous mice are predisposed to tumours in multiple tissues when challenged with γ-irradiation or a chemical carcinogen, therefore p27 is a multiple-tissue tumour suppressor in mice.
Abstract: p27Kip is a candidate human tumour-suppressor protein, because it is able to inhibit cyclin-dependent kinases and block cell proliferation. Abnormally low levels of the p27 protein are frequently found in human carcinomas, and these low levels correlate directly with both histological aggressiveness and patient mortality. However, it has not been possible to establish a causal link between p27 and tumour suppression, because only rare instances of homozygous inactivating mutations of the p27 gene have been found in human tumours. Thus, p27Kip1 does not fulfil Knudson's 'two-mutation' criterion for a tumour-suppressor gene. Here we show that both p27 nullizygous and p27 heterozygous mice are predisposed to tumours in multiple tissues when challenged with gamma-irradiation or a chemical carcinogen. Therefore p27 is a multiple-tissue tumour suppressor in mice. Molecular analyses of tumours in p27 heterozygous mice show that the remaining wild-type allele is neither mutated nor silenced. Hence, p27 is haplo-insufficient for tumour suppression. The assumption that null mutations in tumour-suppressor genes are recessive excludes those genes that exhibit haplo-insufficiency.
795 citations
TL;DR: It is inferred that dE2F and RBF function specifically in cell cycle control, and that cell cycle acceleration is insufficient to stimulate growth.
TL;DR: The described method permits the direct confirmation of drug targets and recognition of drug-dependent changes in gene expression that are modulated through pathways distinct from the drug's intended target.
Abstract: We describe here a method for drug target validation and identification of secondary drug target effects based on genome-wide gene expression patterns. The method is demonstrated by several experiments, including treatment of yeast mutant strains defective in calcineurin, immunophilins or other genes with the immunosuppressants cyclosporin A or FK506. Presence or absence of the characteristic drug 'signature' pattern of altered gene expression in drug-treated cells with a mutation in the gene encoding a putative target established whether that target was required to generate the drug signature. Drug dependent effects were seen in 'targetless' cells, showing that FK506 affects additional pathways independent of calcineurin and the immunophilins. The described method permits the direct confirmation of drug targets and recognition of drug-dependent changes in gene expression that are modulated through pathways distinct from the drug's intended target. Such a method may prove useful in improving the efficiency of drug development programs.
TL;DR: A postinduction course of high-dose cytarabine can provide equivalent disease-free survival and somewhat better overall survival than autologous marrow transplantation in adults with acute myeloid leukemia.
Abstract: Background In young adults with acute myeloid leukemia, intensive chemotherapy during the initial remission improves the long-term outcome, but the role of bone marrow transplantation is uncertain. We compared high-dose cytarabine with autologous or allogeneic marrow transplantation during the first remission of acute myeloid leukemia. Methods Previously untreated adolescents and adults 16 to 55 years of age who had acute myeloid leukemia received standard induction chemotherapy. After complete remission had been achieved, idarubicin (two days) and cytarabine (five days) were administered. Patients with histocompatible siblings were offered allogeneic marrow transplantation, whereas the remaining patients were randomly assigned to receive a single course of high-dose cytarabine or transplantation of autologous marrow treated with perfosfamide (4-hydroperoxycyclophosphamide). Oral busulfan and intravenous cyclophosphamide were used as preparative regimens for both allogeneic and autologous marrow transplan...
TL;DR: Oral SCC risk increased with self-reported decreasing age at first intercourse, increasing number of sex partners, and a history of genital warts, and HPV type 16 infection may contribute to the development of a small proportion of oral SCCs in this population.
Abstract: Background: Experimental models and analyses of human tumors suggest that oncogenic, sexually transmittable human papillomaviruses (HPVs) are etiologic factors in the development of oral squamous cell carcinoma (SCC). We conducted a population-based, case‐control study to determine whether the risk of this cancer is related to HPV infection and sexual history factors. Methods: Case subjects (n = 284) were 18‐65-year-old residents of three counties in western Washington State who were newly diagnosed with oral SCC from 1990 through 1995. Control subjects (n = 477) similar in age and sex were selected from the general population. Serum samples were tested for HPV type 16 capsid antibodies. Exfoliated oral tissue collected from case and control subjects and tumor tissue from case subjects were tested for HPV DNA. Odds ratios (ORs) were calculated after adjusting for age, sex, cigarette smoking, and alcohol consumption. Results: Among males only, oral SCC risk increased with self-reported decreasing age at first intercourse, increasing number of sex partners, and a history of genital warts. Approximately 26% of the tumors in case subjects contained HPV DNA; 16.5% of the tumors contained HPV type 16 DNA. The prevalence of oncogenic HPV types in exfoliated oral tissue was similar in case and control subjects. The ORs for HPV type 16 capsid seropositivity were 2.3 (95% confidence interval [CI] = 1.6‐3.3) for all oral SCCs and 6.8 (95% CI = 3.0‐15.2) for oral SCCs containing HPV type 16 DNA. The joint association of cigarette smoking and HPV type 16 capsid seropositivity with oral SCC (OR = 8.5; 95% CI = 5.1‐14.4) was stronger than predicted from the sum of individual associations with current smoking (OR = 3.2; 95% CI = 2.0‐5.2) and seropositivity (OR = 1.7; 95% CI = 1.1‐2.6). Conclusions: HPV type 16 infection may contribute to the development of a small proportion of oral SCCs in this population, most likely in combination with cigarette smoking. [J Natl Cancer Inst 1998;90:1626‐36]
TL;DR: The finding that HLA class II compatibility of a child was more common for scleroderma patients than for controls, supports the possibility that microchimerism may be involved in the pathogenesis of sclerodma.
TL;DR: expression of a kinase‐inactive allele of ATR in human fibroblasts causes increased sensitivity to ionizing radiation, cis‐platinum and methyl methanesulfonate, but only slight UV radiation sensitivity, which is consistent with uncoupling of certain mitotic events from the completion of S‐phase.
Abstract: ATR, a phosphatidylinositol kinase-related protein homologous to ataxia telangiectasia mutated (ATM), is important for the survival of human cells following many forms of DNA damage. Expression of a kinase-inactive allele of ATR (ATRkd) in human fibroblasts causes increased sensitivity to ionizing radiation (IR), cis-platinum and methyl methanesulfonate, but only slight UV radiation sensitivity. ATRkd overexpression abrogates the G2/M arrest after exposure to IR, and overexpression of wild-type ATR complements the radioresistant DNA synthesis phenotype of cells lacking ATM, suggesting a potential functional overlap between these proteins. ATRkd overexpression also causes increased sensitivity to hydroxyurea that is associated with microtubule-mediated nuclear abnormalities. These observations are consistent with uncoupling of certain mitotic events from the completion of S-phase. Thus, ATR is an important component of multiple DNA damage response pathways and may be involved in the DNA replication (S/M) checkpoint.
TL;DR: An early AR is associated with an increased risk of adult obesity independent of parent obesity and the BMI at AR, and future research should examine the biological and behavioral determinants of AR.
Abstract: Objective. At 5 to 6 years of age, body fatness normally declines to a minimum, a point called adiposity rebound (AR), before increasing again into adulthood. We determined whether a younger age at AR was associated with an increased risk of adult obesity and whether this risk was independent of fatness at AR and parent obesity. Design. A retrospective cohort study using lifelong height and weight measurements recorded in outpatient medical records. Setting. Group Health Cooperative of Puget Sound (GHC), a health maintenance organization based in Seattle, Washington. Participants. All 390 GHC members (and their parents) born at GHC between January 1, 1965, and January 1, 1971, who had at least one recorded adult height and weight measurement plus two visits with recorded height and weight measurements in each of three age intervals: 1.5 to 4, 4 to 8, and 8 to 16 years. Main Outcome Measures. We calculated the mean body mass index (BMI) of each subject during young adulthood (age 21 to 29 years) and the BMI of the parents when each subject was 1.5 years of age. Adult obesity was defined as a BMI ≥27.8 for males and ≥27.3 for females. Curves were fit to each subject9s BMI values between ages 1.5 and 16 years, and the age and BMI at AR were calculated from these curves. Subjects were divided into tertiles of age at AR (early, middle, and late), BMI at AR, and parent BMI (heavy, medium, and lean). Results. The mean age at AR was 5.5 years, and 15% of the cohort was obese in young adulthood. Adult obesity rates were higher in those with early versus late AR (25% vs 5%), those who were heavy versus lean at AR (24% vs 4%), those with heavy versus lean mothers (25% vs 5%), and those with heavy versus lean fathers (21% vs 5%). After adjusting for parent BMI and BMI at AR, the odds ratio for adult obesity associated with early versus late AR was 6.0 (95% CI, 1.3–26.6). Conclusion. An early AR is associated with an increased risk of adult obesity independent of parent obesity and the BMI at AR. Future research should examine the biological and behavioral determinants of AR.
TL;DR: Evidence is provided that expression of the viral genome is optimal in the G2 phase of the cell cycle, and that Vpr increases virus production by delaying cells at the point of thecell cycle where the long terminal repeat (LTR) is most active.
Abstract: The human immunodeficiency virus type 1 (HIV-1) encodes a protein, called Vpr, that prevents proliferation of infected cells by arresting them in G2 of the cell cycle. This Vpr-mediated cell-cycle arrest is also conserved among highly divergent simian immunodeficiency viruses, suggesting an important role in the virus life cycle. However, it has been unclear how this could be a selective advantage for the virus. Here we provide evidence that expression of the viral genome is optimal in the G2 phase of the cell cycle, and that Vpr increases virus production by delaying cells at the point of the cell cycle where the long terminal repeat (LTR) is most active. Although Vpr is selected against when virus is adapted to tissue culture, we show that selection for Vpr function in vivo occurs in both humans and chimpanzees infected with HIV-1. These results suggest a novel mechanism for maximizing virus production in the face of rapid killing of infected target cells.
Journal Article•
TL;DR: The findings suggest that the effects of H. pylori strains on tumor development vary by anatomical site, and may be associated with the rising incidence of esophageal/gastric cardia adenocarcinomas in industrialized countries.
Abstract: Gastric colonization with Helicobacter pylori , especially cagA + strains, is a risk factor for noncardia gastric adenocarcinoma, but its relationship with gastric cardia adenocarcinoma is unclear. Although incidence rates for noncardia gastric adenocarcinoma have declined steadily, paralleling a decline in H. pylori prevalence, rates for adenocarcinomas of esophagus and gastric cardia have sharply increased in industrialized countries in recent decades. To clarify the role of H. pylori infection in these tumors with divergent incidence trends, we analyzed serum IgG antibodies to H. pylori and to a recombinant fragment of CagA by antigen-specific ELISA among 129 patients newly diagnosed with esophageal/gastric cardia adenocarcinoma, 67 patients with noncardia gastric adenocarcinoma, and 224 population controls. Cancer risks were estimated by odds ratios (OR) and 95% confidence intervals (CI) using logistic regression models. Infection with cagA + strains was not significantly related to risk for noncardia gastric cancers (OR, 1.4; CI, 0.7–2.8) but was significantly associated with a reduced risk for esophageal/cardia cancers (OR, 0.4; CI, 0.2–0.8). However, there was little association with cagA - strains of H. pylori for either cancer site (OR, 1.0 and 1.1, respectively). These findings suggest that the effects of H. pylori strains on tumor development vary by anatomical site. Further studies are needed to confirm these results and to assess whether the decreasing prevalence of H. pylori , especially cagA + strains, may be associated with the rising incidence of esophageal/gastric cardia adenocarcinomas in industrialized countries.
TL;DR: The cloning and sequencing of a second AAV3 genome and a new AAV serotype designated AAV6 that is related to AAV1 are reported, suggesting that vectors based on alternative Aav serotypes will have advantages over existing AAV2 vectors, including the transduction of different cell types, and resistance to neutralizing antibodies against AAV 2.
Abstract: Adeno-associated viruses (AAVs) are single-stranded dependent parvoviruses being developed as transducing vectors. Although at least five serotypes exist (AAV types 1 to 5 [AAV1 to -5]), only AAV2, AAV3, and AAV4 have been sequenced, and the vectors in use were almost all derived from AAV2. Here we report the cloning and sequencing of a second AAV3 genome and a new AAV serotype designated AAV6 that is related to AAV1. AAV2, AAV3, and AAV6 were 82% identical at the nucleotide sequence level, and AAV4 was 75 to 78% identical to these AAVs. Significant sequence variation was noted in portions of the capsid proteins that presumably are responsible for serotype-specific functions. Vectors produced from AAV3 and AAV6 differed from AAV2 vectors in host range and serologic reactivity. The AAV3 and AAV6 vector serotypes were able to transduce cells in the presence of serum from animals previously exposed to AAV2 vectors. Our results suggest that vectors based on alternative AAV serotypes will have advantages over existing AAV2 vectors, including the transduction of different cell types, and resistance to neutralizing antibodies against AAV2. This could be especially important for gene therapy, as significant immunity against AAV2 exists in human populations and many protocols will likely require multiple vector doses.
Journal Article•
TL;DR: Analysis of peptides bound to HLA-E revealed that a nonamer peptide derived from the A2 signal sequence was the predominant peptide bound, and was nearly identical to the leader sequence-derived peptide previously shown to be a predominant Peptide bound to the murine Qa-1 Ag.
Abstract: Previous studies showed that HLA-E was expressed in lymphoblastoid cell line (LCL) 721.221 cells, but surface expression was lacking. To determine the signals controlling surface expression, we constructed a series of hybrid genes using complementary portions derived from the HLA-E and HLA-A2 genes. In this manner, a hybrid of HLA-E was identified, designated AEH, which differed from HLA-E by having the HLA-A2 signal sequence substituting for the HLA-E leader peptide. Transfection of LCL 721.221 cells with AEH induced HLA-E surface expression. Analysis of peptides bound to HLA-E revealed that a nonamer peptide derived from the A2 signal sequence was the predominant peptide bound. LCL 721.221 cells transfected with certain class I genes, including HLA-G, were also sufficient to promote peptide binding and HLA-E surface expression without increasing the level of HLA-E heavy chain synthesis. Peptides bound to HLA-E consisted of nine amino acids, with methionine at position 2 and leucine in the carboxyl-terminal position, and were nearly identical to the leader sequence-derived peptide previously shown to be a predominant peptide bound to the murine Qa-1 Ag. Signal peptides derived from certain HLA-B proteins with threonine in position 2 only marginally up-regulated HLA-E surface expression in .221 cells. An examination of HLA-E peptide binding in the TAP negative cell line .134 indicated that peptide binding to HLA-E was dependent on a functional TAP heterodimer regardless of whether peptide was available in cis, as in the AEH construct, or in trans, as in the class I transfectants of .221 cells.
TL;DR: A genetic screen to identify genes whose overexpression disrupts telomeric silencing isolated 10 DOT genes, which include both components and regulators of silent chromatin, suggesting that DOT1 and DOT4 normally play important roles in gene repression.
Abstract: The ends of chromosomes in Saccharomyces cerevisiae initiate a repressive chromatin structure that spreads internally and inhibits the transcription of nearby genes, a phenomenon termed telomeric silencing. To investigate the molecular basis of this process, we carried out a genetic screen to identify genes whose overexpression disrupts telomeric silencing. We thus isolated 10 DOT genes (disruptor of telomeric silencing). Among these were genes encoding chromatin component Sir4p, DNA helicase Dna2p, ribosomal protein L32, and two proteins of unknown function, Asf1p and Ifh1p. The collection also included genes that had not previously been identified: DOT1, DOT4, DOT5, DOT6, and TLC1, which encodes the RNA template component of telomerase. With the exception of TLC1, all these genes, particularly DOT1 and DOT4, also reduced silencing at other repressed loci (HM loci and rDNA) when overexpressed. Moreover, deletion of the latter two genes weakened silencing as well, suggesting that DOT1 and DOT4 normally play important roles in gene repression. DOT1 deletion also affected telomere tract length. The function of Dot1p is not known. The sequence of Dot4p suggests that it is a ubiquitin-processing protease. Taken together, the DOT genes include both components and regulators of silent chromatin.
TL;DR: A fundamental difference in the control of cell cycle activation and maintenance in these two cell types is demonstrated, and the existence of a novel mitogen generated by the larval fat body in response to nutrition is implied.
Abstract: In newly hatched Drosophila larvae, quiescent cells reenter the cell cycle in response to dietary amino acids. To understand this process, we varied larval nutrition and monitored effects on cell cycle initiation and maintenance in the mitotic neuroblasts and imaginal disc cells, as well as the endoreplicating cells in other larval tissues. After cell cycle activation, mitotic and endoreplicating cells respond differently to the withdrawal of nutrition: mitotic cells continue to proliferate in a nutrition-independent manner, while most endoreplicating cells reenter a quiescent state. We also show that ectopic expression of Drosophila Cyclin E or the E2F transcription factor can drive quiescent endoreplicating cells, but not quiescent imaginal neuroblasts, into S-phase. Conversely, we demonstrate that quiescent imaginal neuroblasts, but not quiescent endoreplicating cells, can be induced to enter the cell cycle when co-cultured with larval fat body in vitro. These results demonstrate a fundamental difference in the control of cell cycle activation and maintenance in these two cell types, and imply the existence of a novel mitogen generated by the larval fat body in response to nutrition.
TL;DR: The data suggest that cdk2 activation, through caspase-mediated cleavage of cdk inhibitors, may be instrumental in the execution of apoptosis following casp enzyme activation.
TL;DR: Human immunodeficiency virus type-1 manipulates fundamental host cell processes in sophisticated ways to achieve optimum replicative efficiency and provides new insights into central questions of virology and host cell biology.
Abstract: Human immunodeficiency virus type-1 (HIV-1) manipulates fundamental host cell processes in sophisticated ways to achieve optimum replicative efficiency. Recent studies have provided new details on the molecular interactions of HIV-1 with its host cell. For example, HIV-1 encodes a protein that regulates transcriptional elongation by interacting with a cellular cyclin-dependent kinase, another that activates the specific nuclear export of viral RNA, and several others that affect the intracellular trafficking of viral and host cell proteins. Detailed analysis of the interplay between these viral proteins and normal cellular activities has provided new insights into central questions of virology and host cell biology.
TL;DR: In this paper, the authors discuss methodological aspects of currently used quantitative assays for cytomegalovirus (CMV) (i.e., viral culture techniques, antigen detection, DNA detection assays including PCR, branched-DNA assay, and the DNA hybrid capture assay) and address the correlation of systemic and site-specific CMV load and CMV disease in different populations of immunosuppressed patients as well as the response to antiviral treatment.
Abstract: Cytomegalovirus (CMV) is an important pathogen in transplant recipients and human immunodeficiency virus (HIV)-infected individuals. Major progress has been made in developing quantitative detection methods for CMV in recent years. Due to their high sensitivity, these assays can detect CMV early, and quantitation may be useful in predicting the patient’s risk for disease and in monitoring the effect of antiviral therapy. This review discusses methodological aspects of currently used quantitative assays for CMV (i.e., viral culture techniques, antigen detection assays, DNA detection assays including PCR, branched-DNA assay, and the DNA hybrid capture assay) and addresses the correlation of systemic and site-specific CMV load and CMV disease in different populations of immunosuppressed patients as well as the response to antiviral treatment. To date, direct antigen detection and molecular techniques have largely replaced traditional culture-based techniques for CMV quantitation. In general, a high systemic CMV load is correlated with CMV disease. This correlation is strong in the HIV-infected population and in solid-organ transplant recipients but less clear in allogeneic marrow transplant recipients. Measuring the viral load at specific anatomic sites may be an alternative way to assess disease activity in situations where the systemic viral load correlates poorly with disease activity. A reduction of the systemic CMV load also correlates with a response to antiviral treatment, but more research is needed to evaluate the role of viral load as a surrogate marker for drug resistance. Due to the widespread use of quantitative CMV detection techniques to direct and monitor antiviral treatment, there is a great need for an assessment of the reproducibility of test results and better standardization of the assays.
Journal Article•
TL;DR: Current users of aspirin were at decreased risk of esophageal adenocarcinoma and the risk of cancers of the esophagus and stomach is reduced in users of NSAIDs, although whether the association is causal in nature is not clear.
Abstract: Regular users of aspirin and other nonsteroidal anti-inflammatory drugs (NSAIDs) are at reduced risk of colon cancer, but the evidence for protective effects of NSAIDs elsewhere in the digestive tract is scant. We investigated the association between the use of NSAIDs and risk of esophageal and gastric cancer, using data from a large population-based, case-control study. Cases were individuals, ages 30-79 years, diagnosed with esophageal adenocarcinoma (n = 293), esophageal squamous cell carcinoma (n = 221), gastric cardia adenocarcinoma (n = 261), or noncardia gastric adenocarcinoma (n = 368) in three areas with population-based tumor registries. Controls (n = 695) were selected by random digit dialing and through the rosters of the Health Care Financing Administration. After controlling for the major risk factors, we found that current users of aspirin were at decreased risk of esophageal adenocarcinoma [odds ratio (OR), 0.37; 95% confidence interval (CI), 0.24-0.58], esophageal squamous cell carcinoma (OR, 0.49; 95% CI, 0.28-0.87), and noncardia gastric adenocarcinoma (OR, 0.46; 95% CI, 0.31-0.68), but not of gastric cardia adenocarcinoma (OR, 0.80; 95% CI, 0.54-1.19), when compared to never users. Risk was similarly reduced among current users of nonaspirin NSAIDs. The associations with current NSAID use persisted when we excluded use within 2 or 5 years of reference date, which might have been affected by preclinical disease in cases, and when we restricted analyses to subjects reporting no history of chronic gastrointestinal symptoms. Our findings add to the growing evidence that the risk of cancers of the esophagus and stomach is reduced in users of NSAIDs, although whether the association is causal in nature is not clear.
TL;DR: The structure and location of the allosteric activator site agrees with the pattern of alternate genetic splicing of the PK gene in multicellular eukaryotes that distinguishes between a non-regulated isozyme and the regulated fetal isozymes.
TL;DR: It is shown that mice that do not express L1 have defects in the guidance of axons of the corticospinal tract, a major motor control pathway projecting from the cortex to the spinal cord, and the presence of a ligand for L1, CD24, specifically at the point of decussation suggests a mechanism in which L1 functions to guide corticOSPinal axons across the midline.
TL;DR: This putative catenin–cadherin system is not essential for general cell adhesion in the C. elegans embryo, but rather mediates specific aspects of morphogenetic cell shape change and cytoskeletal organization.
Abstract: During morphogenesis of the Caenorhabditis elegans embryo, hypodermal (or epidermal) cells migrate to enclose the embryo in an epithelium and, subsequently, change shape coordinately to elongate the body (Priess, J.R., and D.I. Hirsh. 1986. Dev. Biol. 117:156– 173; Williams-Masson, E.M., A.N. Malik, and J. Hardin. 1997. Development [Camb.]. 124:2889–2901). We have isolated mutants defective in morphogenesis that identify three genes required for both cell migration during body enclosure and cell shape change during body elongation. Analyses of hmp-1 , hmp-2 , and hmr-1 mutants suggest that products of these genes anchor contractile actin filament bundles at the adherens junctions between hypodermal cells and, thereby, transmit the force of bundle contraction into cell shape change. The protein products of all three genes localize to hypodermal adherens junctions in embryos. The sequences of the predicted HMP-1, HMP-2, and HMR-1 proteins are related to the cell adhesion proteins α-catenin, β-catenin/Armadillo, and classical cadherin, respectively. This putative catenin–cadherin system is not essential for general cell adhesion in the C. elegans embryo, but rather mediates specific aspects of morphogenetic cell shape change and cytoskeletal organization.