Showing papers on "Regulation of gene expression published in 1984"
TL;DR: The development of an immunocytochemical procedure suitable for localizing oestrophilin directly in frozen tissue sections or cells from human and several non-human sources is reported.
Abstract: Although it is widely accepted that specific intracellular receptor proteins are involved in the oestrogenic regulation of gene expression and growth in reproductive tissues, the precise nature of the regulation is poorly understood. Among the unresolved issues are the distribution and dynamics of the oestrogen receptor protein (oestrophilin) in target tissues in the presence and absence of oestrogens and antioestrogens. The use of radio-labelled and unlabelled receptor ligands to detect and measure oestrogen receptors in tissues has been complicated by the presence of other intracellular steroid-binding proteins1 and by the low concentration of receptors in responsive tissues. We report here the development of an immunocytochemical procedure that is suitable for localizing oestrophilin directly in frozen tissue sections or cells from human and several non-human sources. When monoclonal antibodies to oestrophilin were used to detect receptor in various oestrogen-sensitive tissues, specific staining was confined to the nucleus of all stained cells, suggesting that both cytosol and nuclear forms of the receptor protein may reside in the nuclear compartment.
1,404 citations
TL;DR: It is found that there is a B-cell-specific enhancer-activator region in the J-C intron of the human kappa gene that is necessary for efficient transcription of the cloned gene in mouse pre-B lymphocytes, suggesting that both the DNA element and the proteins required for its regulatory activity have been highly conserved in evolution.
Abstract: We have developed a general method for introducing cloned genes into mammalian cells that affords substantial benefits over current technology. It is simple, rapid, and applicable to many (perhaps all) cell types, including those that are refractory to traditional transfection procedures. The method involves exposure of a suspension of cells and cloned DNA to a high-voltage electric discharge. In a model application of this transfection procedure, we have studied the expression of cloned human and mouse Ig kappa genes stably introduced into mouse pre-B cells and fibroblasts. We find that there is a B-cell-specific enhancer-activator region in the J-C intron of the human kappa gene that is necessary for efficient transcription of the cloned gene in mouse pre-B lymphocytes. This suggests that both the DNA element and the proteins required for its regulatory activity have been highly conserved in evolution and that these elements operate at the pre-B-cell stage of immunocyte development, a stage that precedes productive kappa gene rearrangement.
928 citations
583 citations
TL;DR: While the REP sequences do not appear to modulate differential gene expression within an operon, they can affect the expression of both upstream and downstream genes to a small extent, probably by affecting the rate of mRNA degradation.
577 citations
TL;DR: It is demonstrated that primary papillomas induced by chemical carcinogens in two different mouse strains have an activated c-rasH gene, the first report of a benign tumour which contains DNA with detectable transforming activity.
Abstract: An important feature of the development of many human and animal tumours is the appearance of pre-malignant benign lesions, some of which undergo further changes during progression to malignancy. Many of the currently accepted concepts of multi-stage carcinogenesis have been developed using an experimental model based on the chemical induction of tumours in mouse skin. In this system, many of the premalignant papillomas which arise are promoter-dependent, and appear to regress if promoter treatment is interrupted, whereas others progress to form autonomous benign lesions and, in some cases, malignant carcinomas. Although the number and nature of the events leading to malignancy are not known, DNA transfection experiments have led to the identification of several genes which may be qualitatively altered in tumour cells (see ref. 6 for review). We have previously shown that DNA from transplantable mouse skin carcinomas induced by chemical carcinogens has the ability to transform NIH/3T3 cells, and that the gene responsible for the transformation is an activated form of the mouse cellular Harvey-ras gene (c-rasH). We have now investigated the stage of carcinogenesis at which the proto-oncogene acquires transforming activity. We demonstrate that primary papillomas induced by chemical carcinogens in two different mouse strains have an activated c-rasH gene. This constitutes the first report of a benign tumour which contains DNA with detectable transforming activity. In addition, steady-state levels of c-rasH gene transcripts are elevated in the papillomas as compared with normal epidermis.
537 citations
TL;DR: The results show that the expression of c-myb and c- myc, at the level of transcription, decreases only at late stages in the monocytic differentiation of WEHI-3B cells, while expression ofc-fos increases markedly, suggesting that c-Myb andc-myc function in the maintenance of the proliferative state of myeloid cells.
Abstract: It is widely thought that c-onc genes (or proto-oncogenes)—the cellular progenitors of retroviral transforming genes—are involved in cellular differentiation and/or proliferation. Such ideas originate primarily from the ability of v-onc genes and ‘activated’ c-onc genes to induce uncontrolled cellular proliferation, and their capacity to arrest or interfere with differentiation processes in some systems. Haematopoietic cell populations provide additional support for these ideas as c-myb RNA is present in cell lines corresponding to immature, but not mature, cell types1,2, and elevated levels have been found in tissues that are active in haematopoiesis2,3. We have now examined the effects of induced differentiation on c-onc gene expression in a murine myeloid leukaemia cell line, WEHI-3B (‘D+’ subline)4. Our results show that the expression of c-myb and c-myc, at the level of transcription, decreases only at late stages in the monocytic differentiation of WEHI-3B cells, while expression of c-fos increases markedly. We suggest that c-myb and c-myc do not themselves control myeloid differentiation, but that they function in the maintenance of the proliferative state of myeloid cells. The induction of c-fos may reflect its role in some macrophage-specific functions.
510 citations
TL;DR: In tumor cell lines having alterations at the c-myc locus due to amplification or translocation, a significant change in the expression of p64 relative to p67 is observed when compared with normal or Epstein-Bar virus-immortalized cells.
Abstract: To examine myc protein products in the wide variety of human tumor cells having alterations of the c-myc locus, we have prepared an antiserum against a synthetic peptide corresponding to the predicted C-terminal sequence of the human c-myc protein. This antiserum (anti-hu-myc 12C) specifically precipitated two proteins of 64 and 67 kilodaltons in quantities ranging from low levels in normal fibroblasts to 10-fold-higher levels in Epstein-Barr virus-immortalized and Burkitt's lymphoma cell lines, to 20- to 60-fold-higher levels in cell lines having amplified c-myc. The p64 and p67 proteins were found to be highly related by partial V8 proteolytic mapping, and both were demonstrated to be encoded by the c-myc oncogene, using hybrid-selected translation of myc-specific RNA. In addition, the p64 protein was specifically precipitated from cells transfected with a translocated c-myc gene. Both p64 and p67 were found to be nuclear phosphoproteins with extremely short half-lives. In tumor cell lines having alterations at the c-myc locus due to amplification or translocation, we observed a significant change in the expression of p64 relative to p67 when compared with normal or Epstein-Bar virus-immortalized cells.
500 citations
TL;DR: When linked to transcriptional enhancers, the mutant Ha-ras-1 gene from the T24 bladder carcinoma cell line induces the complete malignant transformation of early passage cells, while the normal Haras- 1 proto-oncogene only induces immortalization as discussed by the authors.
Abstract: When linked to transcriptional enhancers, the mutant Ha-ras-1 gene from the T24 bladder carcinoma cell line induces the complete malignant transformation of early passage cells, while the normal Ha-ras-1 proto-oncogene only induces immortalization. Therefore, mutated Ha-ras-1 does not require a cooperating gene to trigger malignant conversion and ras genes may be involved in the process of tumorigenesis at an earlier stage than previously suspected.
445 citations
TL;DR: Inhibition of protein synthesis resulted in a dramatic stabilization of myc mRNA in HeLa, MCF7, and HL60 cells, suggesting that the controlling element might itself be, at least in these cells, a protein of rapid turnover.
Abstract: To address the possibility that the expression of the myc gene might be regulated at a post-transcriptional level, we have investigated the half-life of myc mRNA in various cells Our survey included normal human embryonic fibroblasts as well as transformed human cells of various origins: cervix carcinoma (HeLa), breast carcinoma (MCF7), Burkitt lymphoma (Daudi), and promyelocytic leukemia (HL60) All these cells revealed an extreme instability of myc mRNA (half-life, approximately equal to 10 min), suggesting that the control of myc mRNA degradation might be a general means (although not necessarily exclusive) of regulating both the level and the timing of myc gene expression Inhibition of protein synthesis resulted in a dramatic stabilization of myc mRNA in HeLa, MCF7, and HL60 cells, suggesting that the controlling element might itself be, at least in these cells, a protein of rapid turnover This finding opens the way to studying the mechanism of myc mRNA inactivation in these different cell types However, protein synthesis inhibition had no effect on myc mRNA instability in other transformed (Daudi) cell lines as well as normal embryonic human fibroblasts These different types of behavior suggest that the post-transcriptional control of myc gene expression might involve multiple factors that would be differently affected in various cell types
439 citations
TL;DR: Comparison of the sequence of the 70Z/3 kappa light chain gene with those encoding other immunoglobulin heavy and light chains has revealed that a distinctive promoter region structure is characteristic of this multigene family.
Abstract: Recent investigations have suggested that tissue-specific regulatory factors are required for immunoglobulin gene transcription. Cells of the mouse lymphocytoid pre-B-cell line 70Z/3 contain a constitutively rearranged immunoglobulin kappa light chain gene; the nucleotide sequence of this gene exhibits all the known properties of a functionally competent transcription unit. Nevertheless, transcripts derived from this gene are detectable only after exposure of the cells to bacterial lipopolysaccharide, implying that accurate DNA rearrangement is not sufficient to activate expression of the gene. Comparison of the sequence of the 70Z/3 kappa light chain gene with those encoding other immunoglobulin heavy and light chains has revealed that a distinctive promoter region structure is characteristic of this multigene family. The sequence A-T-T-T-G-C-A-T lies approximately 70 base pairs upstream from the site of transcriptional initiation in every light chain gene examined; in heavy chain genes, the corresponding location is occupied by the precise inverse (A-T-G-C-A-A-A-T) of this sequence. Although adjacent regions of DNA have diverged extensively in evolution, these octanucleotide sequences are stringently conserved at this location among diverse immunoglobulin genes from at least two mammalian species. The proximity of this conserved octanucleotide block to the site of transcriptional initiation suggests that it may serve as a recognition locus for factors regulating immunoglobulin gene expression in a tissue-specific fashion.
405 citations
TL;DR: There appear to be three cytoplasmic polyadenylated RNA products of EGF receptor gene expression in A431 cells, one of which contains only 5' (EGF binding domain) sequences and is postulated to encode the secreted EGF receptors-related protein.
Abstract: In order to further define the mechanisms by which polypeptide growth factors regulate gene transcription and cellular growth, expression cloning techniques were used to select human epidermal growth factor (EGF) receptor complementary DNA clones. The EGF 3' coding domain shows striking homology to the transforming gene product of avian erythroblastosis virus (v-erbB). Over-expression of EGF receptors in A431 cell lines correlates with increased EGF receptor mRNA levels and amplification (up to 110 times) of the apparently singular EGF receptor gene. There appear to be three cytoplasmic polyadenylated RNA products of EGF receptor gene expression in A431 cells, one of which contains only 5' (EGF binding domain) sequences and is postulated to encode the secreted EGF receptor-related protein.
TL;DR: It is shown here for one patient that N-myc amplification is confined to the neuroblastoma tumor and is not present in normal tissue, and it is hypothesized that amplification and consequent elevated expression of N- myc may be related to malignant progression.
Abstract: Previous studies had revealed that DNA with partial similarity to the myc oncogene (N-myc) is frequently amplified in human neuroblastoma cell lines and neuroblastoma tumors. We show here for one patient that N-myc amplification is confined to the neuroblastoma tumor and is not present in normal tissue. N-myc mRNA approximately equal to 4.0 kilobases in size is detectable in neuroblastoma cell lines and tumors and in a retinoblastoma cell line. By contrast, appreciable amounts of this RNA were not present in a number of cell lines derived from other human tumors and in fibroblasts from a normal individual and from a neuroblastoma patient. Low levels of N-myc RNA were found in human and murine neuroblastoma cell lines lacking amplification of this gene, up to 80-fold greater levels in all cell lines carrying amplified N-myc. In situ hybridization to sections of neuroblastoma tumors revealed high expression of N-myc predominantly in undifferentiated neuroblasts. We hypothesize that amplification and consequent elevated expression of N-myc may be related to malignant progression.
TL;DR: Chicken skeletal muscle myosin alkali light chains are encoded by a single gene of size 18 kilobases (kb), which has two transcription initiation sites from which 17.5- and 8-kb precursor RNAs are transcribed.
Abstract: Chicken skeletal muscle myosin alkali light chains are encoded by a single gene of size 18 kilobases (kb). This gene has two transcription initiation sites from which 17.5- and 8-kb precursor RNAs are transcribed. These RNAs are processed by different modes of splicing to form mRNAs encoding distinct light-chain (LC1 and LC3) proteins.
TL;DR: Direct evidence is shown for a functionally similar enhancer within the large κ gene intron of the mouse which is, however, less active than the heavy-chain gene enhancer.
Abstract: During differentiation of lymphocytes into antibody-producing cells, an immunoglobulin kappa variable-region gene is transcriptionally activated by rearrangement linking it to a kappa constant (C kappa) region gene which is already transcribed prior to somatic rearrangement. The presence of a transcriptional enhancer element within the large intron of the kappa light-chain gene has been postulated to explain this mode of activation, supported by evidence of a chromatin region which is preferentially accessible to DNase I and restriction enzymes. This DNA region contains a segment of about 130 base pairs (bp) which is strongly conserved between mouse, rabbit and man. Moreover, no transcripts are detectable from a kappa gene, which is truncated within the large intron. Recently, a lymphocyte-specific enhancer has been identified downstream of the joining region in immunoglobulin heavy-chain genes. We now show direct evidence for a functionally similar enhancer within the large kappa gene intron of the mouse. It is, however, less active than the heavy-chain gene enhancer. In contrast, no enhancer was found to be associated with a cloned lambda I light-chain gene.
TL;DR: A positive regulatory gene from Vibrio cholerae that controls cholera toxin transcription is cloned by first constructing a genetic fusion consisting of the lacZ gene fused to the promoter of the cholERA toxin operon ctxAB to identify a gene, toxR, that increases ctx expression by more than 100-fold.
Abstract: We have cloned a positive regulatory gene ( toxR ) from Vibrio cholerae that controls cholera toxin transcription. This was done by first constructing a genetic fusion consisting of the lacZ gene fused to the promoter of the cholera toxin operon ctxAB . This operon fusion was used to screen a V. cholerae genomic library for genes that could activate the ctx promoter in Escherichia coli. This method allowed the identification of a gene, toxR , that increases ctx expression by more than 100-fold. Complementation analysis indicated that certain hypotoxinogenic mutants of V. cholerae 569B probably have mutations in the toxR gene. Southern blot analysis suggests that all V. cholerae, including nontoxinogenic strains, have the toxR gene. Moreover, nontoxinogenic strains not only lack the structural genes for cholera toxin but also sequences associated with the larger 7-kilobase ctx genetic element.
TL;DR: Results of these studies show that the enhancer sequence alone is unable to induce gene activity but requires other promoter elements, including a proximal GC-rich sequence and the Goldberg-Hogness box.
Abstract: A series of recombinant molecules were constructed which direct the expression of the easily assayed gene chloramphenicol acetyltransferase. We have used these recombinants to show that the 73/72-base-pair tandem repeat unit from the Moloney murine sarcoma virus long terminal repeat shares a number of properties with the prototypic enhancer element, the simian virus 40 72-base-pair repeat. Specifically, the Moloney murine sarcoma virus sequence significantly enhances the level of gene expression at both 5' and 3' locations and in either orientation relative to the test gene. It is able to enhance gene activity both from its own promoter and from a heterologous (simian virus 40) promoter. The 73/72-base-pair subunits of the Moloney murine sarcoma virus enhancer differ in sequence by four nucleotides and also in the strength of their enhancer function. The promoter distal A repeat is at least three times as active as the promoter proximal B repeat in enhancing chloramphenicol acetyltransferase expression. Results of these studies also show that the enhancer sequence alone is unable to induce gene activity but requires other promoter elements, including a proximal GC-rich sequence and the Goldberg-Hogness box.
TL;DR: The TG-element appeared to have characteristics similar to those of viral enhancers, but its enhancer-like activity was much weaker than that of the simian virus 40 enhancer, and, unlike many viral enhancies, it was equally active in monkey and in human cells.
Abstract: The sequence poly(dT-dG).poly(dC-dA) (TG-element) is a ubiquitous component of eucaryotic genomes and has the potential to adopt a left-handed DNA conformation (Z-DNA). In this report, we have tested the hypothesis that the TG-element can modulate gene expression. Human genomic DNA fragments (1 to 1.5 kilobases) containing a (dT-dG)n.(dC-dA)n tract (30, 40, or 50 base pairs) or chemically synthesized (dT-dG)n.(dC-dA)n fragments (50 to 130 base pairs) were inserted in the pSV2-cat (simian virus 40 enhancer plus) or pA10-cat (enhancer minus) expression vector plasmid. These constructs were transfected into CV-1 cells or HeLa cells, and their transcription was monitored by assaying chloramphenicol acetyltransferase activity. The results showed that pSV2-cat with the TG-element and pA10-cat with the TG-element synthesized more chloramphenicol acetyltransferase activity (2 to 10 times, depending on the location of the TG-element) than did parental pSV2-cat and pA10-cat DNAs, respectively. Furthermore, the TG-element appeared to have characteristics similar to those of viral enhancers: (i) the TG-element enhanced transcription from a distance, (ii) its closer location to the promoter was more effective, and (iii) its orientation was not crucial. However, its enhancer-like activity was much weaker than that of the simian virus 40 enhancer, and, unlike many viral enhancers, it was equally active in monkey and in human cells. These results suggest that the TG-element may influence the expression of cellular genes.
TL;DR: The yeast copper metallothionein regulatory sequences represent a previously unreported class of yeast promoter that is regulated by copper.
Abstract: Addition of copper to yeast cells leads to the induction of a low molecular weight, cysteine-rich protein that binds copper. This protein, termed copper chelatin or thionein, is related to the metallothionein family of proteins that are induced in response to cadmium and zinc in vertebrate cells. We have determined the structure of the yeast copper-binding protein by DNA sequence analysis of the gene. Although the 6573-dalton yeast protein is substantially divergent from vertebrate metallothioneins, the arrangement of 12 cysteine residues, which is a hallmark of metal-binding proteins, is partially conserved. We analyzed the regulatory DNA sequence of the gene by fusing it with the Escherichia coli galactokinase gene and assaying the levels of enzyme activity in yeast in response to copper. The transcriptional activation has a specific requirement for copper. Zinc, cadmium, and gold were unable to regulate the galactokinase activity. The yeast copper metallothionein regulatory sequences represent a previously unreported class of yeast promoter that is regulated by copper.
TL;DR: In this article, a new vector for transformation that carries a fusion of the Dictyostelium discoideum actin 6 promoter gene and 5' flanking region with the bacterial Tn5 NeoR (KanR) gene was constructed.
Abstract: We have constructed a new vector for transformation that carries a fusion of the Dictyostelium discoideum actin 6 promoter gene and 5' flanking region with the bacterial Tn5 NeoR (KanR) gene which can confer resistance to the aminoglycoside G418. This vector can be used to transform D. discoideum cells. Approximately 200 to 2,000 transformants were obtained per 10(7) cells. Transformed cell populations carried vector DNA at an average copy number of ca. 5 per cell, and the DNA was stable for more than 40 generations in the absence of selection. We have shown that transformed cells synthesize functional kanamycin phosphotransferase and that initiation of transcription of the actin 6-NeoR gene fusion occurs at the actin 6 cap site. Moreover, analysis of RNA isolated from transformed and untransformed cells during vegetative growth and during development indicated that the actin 6-NeoR gene fusion was regulated in parallel with the endogenous actin 6 gene, suggesting that the upstream flanking regions of actin 6 contain the cis-acting regulatory sequences sufficient for differential regulation of this gene during D. discoideum development. These results indicate that this system can be used to examine control of gene expression during D. discoideum development.
TL;DR: The gene product of a rearranged mouse c-myc gene is capable of stimulating expression of chimaeric genes containing a Drosophila hSP70 promoter region and 5′-flanking sequences, dependent on sequences located more than 200 bases 5′ of the normal start of hsp70 transcription.
Abstract: The myc gene seems to have a causal role in tumour formation in man, mouse and avian systems1–3. The myc gene product has been localized to the nucleus4,5, suggesting that it may be involved in the regulation of gene expression. The level of expression of the mammalian heat shock protein 70 (HSP70) gene is elevated in several tumour cell lines6, implying that a cellular function expressed in these tumour lines can stimulate HSP70 production. We report here that the gene product of a rearranged mouse c-myc gene is capable of stimulating expression of chimaeric genes containing a Drosophila hsp70 promoter region and 5′-flanking sequences. This stimulation is dependent on sequences located more than 200 bases 5′ of the normal start of hsp70 transcription.
TL;DR: A tissue-specific transcriptional enhancer element that is associated with the human immunoglobulin heavy-chain locus is defined and occurs within sequences shown to activate previously cryptic promoters of the c-myc gene.
Abstract: A tissue-specific transcriptional enhancer element that is associated with the human immunoglobulin heavy-chain locus is defined. In a non-Hodgkin's lymphoma that contains a translocated c-myc gene this enhancer is retained on the 14q+ chromosome and occurs within sequences shown to activate previously cryptic promoters of the c-myc gene.
TL;DR: The data suggest that ras p21 expression is correlated with depth of carcinoma within the bowel wall, and is probably a relatively late event in colon carcinogenesis, as compared with normal colonie epithelium, benign colon tumours and inflammatory or dysplastic colon lesions.
Abstract: DNAS of some human tumours can transform NIH 3T3 fibroblast cells, thus demonstrating the transforming potential of human ras genes (Hu-rasHa, Hu-rasKi, and Hu-rasN, respectively Harvey, Kirsten and neuroblastoma ras genes). Only a small percentage of a given type of human carcinoma, however, scores positive in this assay system. Activation of ras and subsequent transformation of NIH 3T3 cells are either by a point mutation in the ras gene or enhanced expression of the normal, or proto-onc, ras gene. If the transformation of a given human tumour involves the enhanced expression of the normal or cellular ras gene and the resulting gene product, the tumour DNA would probably score negative in the NIH 3T3 transfection assay. In human colon carcinoma, for example, lesions at position 12 of Hu-rasKi have been found. None of nine colon carcinomas obtained at biopsy, however, contain the ras lesion at this position, using a Hu-rasHa probe; one other colon carcinoma does appear to contain amplified proto-onc ras, and other colon carcinomas do have increased levels of ras RNA. There are at least three explanations for these observations. Either very few colon carcinomas contain point-mutated ras, the lesion in the majority of colon carcinomas is at a position other than 12 or ras activation in many colon carcinomas involves the enhanced expression of either the point-mutated or proto-onc form of a ras gene. We have now used monoclonal antibodies directed against a synthetic peptide reflecting sequences of the human T24 ras gene product to define ras p21 protein expression in a spectrum of colonic disease states. Immunohistochemical analyses of individual cells within tissue sections reveal differences in ras p21 expression in colon carcinomas compared with normal colonic epithelium, benign colon tumours and inflammatory or dysplastic colon lesions. Our data suggest that ras p21 expression is correlated with depth of carcinoma within the bowel wall, and is probably a relatively late event in colon carcinogenesis.
TL;DR: Evidence is presented that the human genome possesses an additional relaxin‐related gene (designated human relaxin gene H2) which appears to be selectively expressed in the ovary during pregnancy and which encodes an authentic human Relaxin.
Abstract: In earlier studies we identified in a human genomic library a gene (human relaxin gene H1) coding for a relaxin-related peptide. We now have evidence that the human genome possesses an additional relaxin-related gene (designated human relaxin gene H2) which appears to be selectively expressed in the ovary during pregnancy. Nucleotide sequence analysis revealed striking differences in the predicted structures of relaxin encoded by these two genes. Chemical synthesis of biologically active relaxin based on the sequence obtained from ovarian cDNA clones confirmed that the expressed gene (H2) encodes an authentic human relaxin. The expressed gene appears to be transcribed into two different sized mRNAs and preliminary evidence suggests that the mRNA transcripts possess different 3'-untranslated regions. There was no evidence for the expression of human relaxin gene H1 in the ovary and so far it is unclear whether gene H1 is expressed in another tissue or whether it represents a pseudogene. From the sequence data presented here it will now be possible to construct oligonucleotide probes and raise antibodies against synthetic peptides which could then be used to identify sites of relaxin biosynthesis and specifically quantitate the expression from either the H1 or H2 relaxin genes.
TL;DR: It is shown that repetitive DNA sequences from all derivatives of the two extraembryonic lineages, trophectoderm and primitive endoderm, are substantially undermethylated compared with primitive ectoderm derivatives, which contrasts with the highly methylated state of these repetitive elements observed in adult somatic tissues.
Abstract: Several distinct cell lineages are established during mouse embryogenesis. The trophectoderm and primitive endoderm give rise to extraembryonic structures alone, while the primitive ectoderm becomes the fetus proper. Recent studies suggest that the levels of DNA modification are lower in inactive X chromosomes from extraembryonic tissues than in embryonic and adult somatic tissues. Using HpaII/MspI isoschizomers, Southern blots and cloned probes, we show here that repetitive DNA sequences from all derivatives of the two extraembryonic lineages, trophectoderm and primitive endoderm, are substantially undermethylated compared with primitive ectoderm derivatives. This contrasts with the highly methylated state of these repetitive elements observed in adult somatic tissues. Specific demethylation or inhibition of de novo methylation, or a combination of both mechanisms, may be involved. These findings suggest that elements of gene regulation dependent on DNA modification may be different in extraembryonic cell lineages.
TL;DR: The results indicate that E. coli can alter the rate of synthesis of certain proteins by modulating mRNA stability in response to changes in the rates of cell growth.
Abstract: The rate of production of bacterial gene products is known to vary with the rate of cell growth, the concentrations of many cellular proteins are altered during times of decreased growth rate. In addition, proteins whose in vivo levels show no significant alterations with changes in cell doubling time must be synthesized at rates that vary in direct proportion to the growth rate of the cell. In certain instances, growth-rate dependent gene regulation has been shown to occur at the transcriptional or translational level. Another potentially important element in the regulation of gene expression is the stability of messenger RNA. We report here the effect of bacterial growth rate on the half lives of four different monocistronic Escherichia coli mRNA species. The stabilities of two of these species, the transcripts of the ompA and cat genes, exhibited a marked dependence on cell growth rate, whereas the half lives of the transcripts of the lpp and bla genes are constant over a broad range of cell doubling times. Our results indicate that E. coli can alter the rate of synthesis of certain proteins by modulating mRNA stability in response to changes in the rate of cell growth.
TL;DR: The results show that the transgene is expressed normally and that the production of a complete immunoglobulin molecule turns off light-chain gene rearrangement.
Abstract: Hybridomas were produced from spleen cells of kappa transgenic mice to investigate expression of the transgenic kappa gene, its effect on allelic exclusion and its effect on the control of light-chain gene rearrangement and expression Our results show that the transgene is expressed normally and that the production of a complete immunoglobulin molecule turns off light-chain gene rearrangement
TL;DR: β hCG is shown to arise from β hLH by a series of selected changes with very little neutral drift, and it is concluded that the control for the expression of glycoprotein hormones probably resides in the β subunit genes.
Abstract: Publisher Summary The recombinant DNA technology is used to understand the tissue-specific, developmentally regulated expression of the four different glycoprotein hormones: chorionic gonadotropin (CG), luteinizing hormone (LH), follicle-stimulating hormone (FSH), and thyroid-stimulating hormone (TSH). The isolation of a full-length cDNA encoding the common α subunit demonstrates that there is a single human gene for this protein, expressed in the placenta for production of hCG and in the pituitary for the production of hLH, hFSH, and hTSH. From this, it is concluded that the control for the expression of glycoprotein hormones probably resides in the β subunit genes. The isolation of a full-length cDNA encoding the β subunit of hCG allows to isolate the full human complement of seven hCG β subunit genes or pseudogenes and, by cross-hybridization, the single β hLH gene. The β hLH gene is linked to at least three of the β hCG genes, and together, they show a complex organization of inverted and tandem pairs. In the analysis of independently isolated β hCG cDNA clones and from transfection of six of the seven β hCG genes into mammalian tissue culture cells, it was found that only three of the seven hCG genes are expressed. From a comparison of the nucleotide sequence of two of the β hCG genes and of the single β hLH gene, β hCG is shown to arise from β hLH by a series of selected changes with very little neutral drift.
TL;DR: Different 3' coding exons in the rat calcitonin gene are used to generate distinct mRNAs encoding either the hormone calciton in thyroidal C-cells or a new neuropeptide referred to as calcitonIn gene-related peptide in neuronal tissue, indicating the RNA processing regulation is one strategy used in tissue-specific regulation of gene expression in the brain.
Abstract: Different 3' coding exons in the rat calcitonin gene are used to generate distinct mRNAs encoding either the hormone calcitonin in thyroidal C-cells or a new neuropeptide referred to as calcitonin gene-related peptide in neuronal tissue, indicating the RNA processing regulation is one strategy used in tissue-specific regulation of gene expression in the brain. Although the two mRNAs use the same transcriptional initiation site and have identical 5' terminal sequences, their 3' termini are distinct. The polyadenylation sites for calcitonin and calcitonin gene-related peptide mRNAs are located at the end of the exons 4 and 6, respectively. Termination of transcription after the calcitonin exon does not dictate the production of calcitonin mRNA, because transcription proceeds through both calcitonin and calcitonin gene-related peptide exons irrespective of which mRNA is ultimately produced. In isolated nuclei, both polyadenylation sites appear to be utilized; however, the proximal (calcitonin) site is preferentially used in nuclei from tissues producing calcitonin mRNA. These data suggest that the mechanism dictating production of each mRNA involves the selective use of alternative polyadenylation sites.