Showing papers on "Gene expression published in 1984"
TL;DR: Stimulation of fibroblasts with serum or purified growth factors leads to a dramatic induction of expression of both c-fos mRNA and protein within a few minutes, followed by activation of c-myc.
Abstract: Stimulation of fibroblasts with serum or purified growth factors leads to a dramatic induction of expression of both c-fos mRNA and protein within a few minutes, followed by activation of c-myc. This suggests that c-fos induction is a primary event and the earliest known effect on gene expression by growth factors.
1,283 citations
01 Jan 1984
TL;DR: In this article, le transfert des cellules tumorales en culture le degre de methylation de l'ADN integre of l'adenovirus 12 augmente.
Abstract: L'etat non methyle d'un gene est une condition prealable necessaire mais non suffisante a l'expression. Avec le transfert des cellules tumorales en culture le degre de methylation de l'ADN integre de l'adenovirus 12 augmente
1,024 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
TL;DR: Two stretches of DNA (genetic elements), lying close to the promoter for a human gene for metallothionein, that separately mediate the induction of the gene by heavy metal ions, particularly cadmium, and by glucocorticoid hormones are defined.
Abstract: Deletion experiments have defined two stretches of DNA (genetic elements), lying close to the promoter for a human gene for metallothionein, that separately mediate the induction of the gene by heavy metal ions, particularly cadmium, and by glucocorticoid hormones. The element responsible for induction by cadmium is duplicated, yet a single copy is fully functional; the element responsible for induction by glucocorticoid hormones is coincident with the DNA-binding site for the glucocorticoid hormone receptor.
830 citations
TL;DR: Exposure of quiescent mouse fibroblasts to platelet-derived growth factor induces mRNA from the c-fos proto-oncogene within 10 min followed by synthesis of nuclear c- fos proteins, amongst the earliest described nuclear events that follow a mitogenic stimulus.
Abstract: Exposure of quiescent mouse fibroblasts to platelet-derived growth factor induces mRNA from the c-fos proto-oncogene within 10 min followed by synthesis of nuclear c-fos proteins. These are amongst the earliest described nuclear events that follow a mitogenic stimulus.
813 citations
TL;DR: The human T-cell growth factor (interleukin-2) receptor is purified and cloned, sequenced and expressed cDNAs corresponding to this receptor and one gene, but two interleukIn-2 receptor mRNAs which differ in their polyadenylation signals are identified.
Abstract: We have purified the human T-cell growth factor (interleukin-2) receptor and have cloned, sequenced and expressed cDNAs corresponding to this receptor. We identify one gene, but two interleukin-2 receptor mRNAs which differ in their polyadenylation signals. We have isolated an additional cDNA that may correspond to an alternatively spliced mRNA that lacks a 216 base segment and appears to encode an altered membrane protein which cannot bind interleukin-2.
787 citations
TL;DR: The cloning, sequence analysis and expression of murine IL-1 cDNA in Escherichia coli reveals a polypeptide precursor of 270 amino acids that may play a major role in the initiation and amplification of immune and inflammatory responses through its action on these diverse cell populations.
Abstract: Interleukin-1 (IL-1), a peptide hormone produced by activated macrophages, possesses the ability to modulate the proliferation, maturation and functional activation of a broad spectrum of cell types1–7 and may play a major role in the initiation and amplification of immune and inflammatory responses through its action on these diverse cell populations8. IL-1 exhibits microheterogeneity in terms of its relative molecular mass (Mr, 13,000–19,000) and charge properties8, and although murine IL-1 has been purified9,10 and some of its basic structure–function relationships have been elucidated8, it has proved difficult to prepare sufficient amounts of IL-1 for direct and detailed sequence and structural studies. Here we report the cloning, sequence analysis and expression of murine IL-1 cDNA in Escherichia coli. The IL-1 cDNA codes for a polypeptide precursor of 270 amino acids. Biologically active IL-1 was produced in E. coli by expressing the carboxy-terminal 156 amino acids of the IL-1 precursor.
778 citations
TL;DR: It is proposed that the micRNA inhibits the translation of the ompF mRNA by hybridizing with it and this RNA interaction may cause premature termination of the transcription of theOmpF gene or destabilization of the OmpF RNA or both.
Abstract: The expression of the genes for the major outer membrane proteins OmpF and OmpC are osmoregulated. The ompC locus was found to be transcribed bidirectionally under conditions of high osmolarity and a 174-base transcript encoded upstream of ompC was found to inhibit the OmpF production and to substantially reduce the amount of the ompF mRNA. This RNA [mRNA-interfering complementary RNA (micRNA)] has a long sequence that is complementary to the 5' end region of the ompF mRNA. We propose that the micRNA inhibits the translation of the ompF mRNA by hybridizing with it. This RNA interaction may cause premature termination of the transcription of the ompF gene or destabilization of the ompF mRNA or both.
654 citations
TL;DR: Eighteen cDNAs, cloned from interferon-treated T98G neuroblastoma cells, correspond to seven different mRNAs induced up to 40-fold by interferons, and one codes for metallothionein II and another for a class I HLA.
647 citations
TL;DR: Data suggest a relatively selective action of CsA on TCGF gene transcription, which is at least in part due to inhibition of lymphokine production by activated T lymphocytes.
Abstract: Cyclosporin A (CsA) is a potent immunosuppressive agent, now gaining wide application in human organ transplantation. The immunosuppressive activity of CsA is at least in part due to inhibition of lymphokine production by activated T lymphocytes. Specifically, inhibition of T-cell growth factor (TCGF; also designated interleukin 2) production appears to be an important pathway by which CsA impairs T-cell function. To define further both the specificity of CsA and the level at which it interferes with lymphokine gene expression, we have studied its effects on TCGF mRNA accumulation as well as TCGF gene transcription. These studies were performed with a cloned human leukemic T-cell line (Jurkat, subclone 32), which can be induced with phytohemagglutinin and phorbol 12-myristate 13-acetate to produce large amounts of TCGF. In these cells, high levels of TCGF mRNA were present in induced but not in uninduced Jurkat cells as judged by hybridization to a cloned human TCGF cDNA probe. CsA completely inhibited induced TCGF mRNA accumulation at concentrations of 0.3-1.0 microgram/ml, whereas low levels of appropriately sized TCGF mRNA were present at 0.01 microgram/ml. In nuclear transcription experiments, CsA inhibited the synthesis of TCGF transcripts in a dose-dependent manner with complete inhibition at a concentration of 1 microgram/ml. In contrast, CsA did not inhibit the expression of two other inducible genes, TCGF receptor and HT-3. Further, HLA gene expression was also less affected than TCGF in CsA-treated cells. These data suggest a relatively selective action of CsA on TCGF gene transcription.
579 citations
TL;DR: Cells contransformed with flipped TK gene constructions have a reduced capacity to express subsequently microinjected TK genes, suggesting that the anti-message phenomenon is due to a trans-inhibition of TK and is probably not an artifact of rearrangements following microinjection.
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.
TL;DR: Comparison of DNA from tumor tissue (or cell lines derived from tumors) with DNA from unaffected tissues reveals structural rearrangements as well as changes in DNA methylation of the foreign DNA.
TL;DR: A new species of T-cell receptor cDNA clone whose predicted amino acid sequence has homology to variable, constant, joining and diversity segments of immunoglobulins and T- cell receptors is isolated.
Abstract: By subtractive cDNA hybridizations, we have isolated a new species of T-cell receptor cDNA clone whose predicted amino acid sequence has homology to variable, constant, joining and diversity segments of immunoglobulins and T-cell receptors. The corresponding genomic sequence is also rearranged in several T-cell DNAs. The four potential N-linked glycosylation sites, frequency of expression and predicted molecular weight (27,800) of this molecule make it a likely candidate for the alpha-chain of the T-cell receptor. Expression data also indicate that this gene may be activated at a later stage of T-cell differentiation than the beta-chain.
TL;DR: A synthetic 21-base-pair long DNA fragment containing the central lac operator sequence has been inserted near the initiation point of the cloned Escherichia coli rrnB rRNA promoter P2 in the natural and reverse orientation.
Abstract: A synthetic 21-base-pair long DNA fragment containing the central lac operator sequence has been inserted near the initiation point of the cloned Escherichia coli rrnB rRNA promoter P2 in the natural and reverse orientation. RNA synthesis is efficiently repressed in both orientations in lac Iq strains and is induced with isopropyl beta-D-thiogalactoside. When the rrnB promoter P1 is also present, upstream from P2 and the synthetic lac operator, repression of transcription is incomplete. The levels of transcription were measured in vivo, indirectly by the expression of a protein (chloramphenicol acetyltransferase), or directly by the expression of a stable RNA (E. coli 4.5S RNA) in a simple assay involving gel electrophoresis of unlabeled total RNA from E. coli. The rrnB promoter constructions can produce high levels of protein expression as well as high levels of expression of stable RNA.
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
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: The resistance to exonuclease digestion of two regions of chromatin at the 5′ end of heat-shock genes in Drosophila implies they have protein bound to them.
Abstract: The resistance to exonuclease digestion of two regions of chromatin at the 5′ end of heat-shock genes in Drosophila implies they have protein bound to them. The pattern of resistance before and after induction of gene expression suggests that heat-shock genes are activated by the sequential binding of at least two protein factors.
TL;DR: Under low stringency conditions, the mouse v-fos gene cross-hybridizes with the PDGF-inducible complementary DNA clone, however, the messenger RNA transcripts of mouse c- fos and the new fos-related gene can be distinguished by gel electrophoresis and by S1 nuclease analysis.
Abstract: Complementary DNA clones of genes induced by platelet-derived growth factor (PDGF) in BALB/c-3T3 cells were isolated; one such clone contains a domain having nucleotide sequence homology with the third exon of c-fos. This nucleotide sequence homology is reflected in the predicted amino acid sequences of the gene products. Under low stringency conditions, the mouse v-fos gene cross-hybridizes with the PDGF-inducible complementary DNA clone. However, the messenger RNA transcripts of mouse c-fos and the new fos-related gene can be distinguished by gel electrophoresis and by S1 nuclease analysis. Expression of the authentic c-fos gene is induced by PDGF and superinduced by the combination of PDGF and cycloheximide.
TL;DR: The level of c-myc messenger RNA shows a rapid biphasic change in MEL cells induced to differentiate by dimethyl sulphoxide or hypoxanthine during the first few hours of the differentiation programme and require active protein synthesis, suggesting that changes in c- myc expression may be important in the irreversible commitment of M EL cells to terminal erythroid differentiation.
Abstract: The transforming gene of avian myelocytomatosis virus MC29, v-myc, causes a variety of malignancies in chickens. A cellular homologue, c-myc, has been implicated in B-cell malignancies in mice and humans but is also expressed in many normal cell types and may be important in the control of normal cell proliferation. c-myc is highly conserved in vertebrates. We have been investigating the relationship between c-myc expression and the terminal differentiation of cultured mouse erythroleukaemia (MEL) cells. We find that the level of c-myc messenger RNA shows a rapid biphasic change in MEL cells induced to differentiate by dimethyl sulphoxide or hypoxanthine. The changes occur during the first few hours of the differentiation programme and require active protein synthesis. These data suggest that changes in c-myc expression may be important in the irreversible commitment of MEL cells to terminal erythroid differentiation.
TL;DR: T lymphocytes can produce mRNAs from the first or second constant region of the T-cell antigen receptor β-chain, which contains V, J and one of the two C region sequences, but does not always contain D sequences.
Abstract: T lymphocytes can produce mRNAs from the first or second constant region of the T-cell antigen receptor β-chain. A 1.3-kilobase (kb) transcript encoding the mature protein contains V, J and one of the two C region sequences, but does not always contain D sequences. A 1.0-kb mRNA, found mainly in immature T cells, does not contain V sequences and can result from transcription that initiates upstream from an unrearranged J element.
TL;DR: The DNA fragment coding for the signal peptide of the OmpA protein, a major outer membrane protein of Escherichia coli, has been inserted into the high‐level expression vectors, pIN‐III and upon induction of gene expression, beta‐lactamase with the authentic NH2‐terminal sequence was produced, in even larger amounts than the beta‐fraction with the linker sequence.
Abstract: The DNA fragment coding for the signal peptide of the OmpA protein, a major outer membrane protein of Escherichia coli, has been inserted into the high-level expression vectors, pIN-III. A foreign DNA fragment can be cloned in any one of the three reading frames at the unique EcoRI, HindIII or BamHI sites immediately after the ompA signal peptide coding sequence. The cloned foreign gene is under the control of both the lpp promoter and the lac promoter-operator. The expression of the gene is regulated by the lac repressor produced by the same vectors. Using the pIN-III-ompA vector, the DNA fragment coding for only the mature portion of beta-lactamase was inserted into the EcoRI site. Upon induction of gene expression, beta-lactamase was secreted into the periplasmic space. The ompA signal peptide was correctly removed resulting in the production of beta-lactamase with four extra amino acid residues (Gly-Ile-Pro-Gly) at its amino terminus due to the linker sequence in the vector. After a 3-h induction, beta-lactamase was accumulated to 20% of total cellular protein without any detectable accumulation of pro-beta-lactamase. Using oligonucleotide-directed site-specific mutagenesis, we have also removed the linker sequence and upon induction of gene expression, beta-lactamase with the authentic NH2-terminal sequence was produced, in even larger amounts than the beta-lactamase with the linker sequence.
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.
Patent•
13 Apr 1984
TL;DR: The phaseolin structural gene and its promoter were disposed in this article, and plasmids, bacteria, plant cells, plant tissue and plants containing the phaseolin promoter were disclosed.
Abstract: The phaseolin structural gene and promoter are disposed. Also disclosed are plasmids, bacteria, plant cells, plant tissue and plants containing the phaseolin promoter. The promoter finds use in the expression of heterologous plants genes, including the phaseolin gene, in transformed plant cells and plants.
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: A chimaeric gene, consisting of the 5′-flanking region of a member of the Pisum sativum gene family encoding ribulose 1,5-bisphosphate carboxylase linked to the coding area of a bacterial chloramphenicol acetyltransferase gene, has been introduced into the genome of the plant Nicotiana tabacum using a Ti plasmid of Agrobacterium tumefaciens.
Abstract: A chimaeric gene, consisting of the 5'-flanking region of a member of the Pisum sativum gene family encoding ribulose 1,5-bisphosphate carboxylase linked to the coding region of a bacterial chloramphenicol acetyltransferase gene, has been introduced into the genome of the plant Nicotiana tabacum using a Ti plasmid of Agrobacterium tumefaciens The expression of the chimaeric gene is light-inducible in chloroplast-containing transformed tissue
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: Hybridization analysis of in-vitro transcription products made in nuclei isolated from untreated and auxin-treated soybean primary leaves and excised hypocotyl sections indicates that, for the two cDNA clones analyzed, the increased RNA levels in auxIn-treated organs are at least partially the result of increased transcriptional activity of specific DNA sequences.
Abstract: A library of complementary DNA (cDNA) clones has been prepared from polyadenylated RNA (poly(A)(+)RNA) from auxin (2,4-dichlorophenoxyacetic acid)-treated soybean (Glycine max (L.) Merr. cv. Wayne) seedlings. Using differential hybridization, four clones were selected as auxin-responsive, and characterized. The levels of the RNA sequences homologous to the cDNA clones were examined in the hypocotyl of the intact seedling and in excised hypocotyl sections before and after auxin treatment, using RNA blot hybridization analysis. RNA levels are rapidly increased (within 0.25-0.5 h) following auxin treatment and the response in the hypocotyl of the intact seedling is transient, reaching maximum RNA levels 2-4 h after auxin application. Increases in RNA levels were also observed with the auxins indole 3-acetic acid and 2,4,5-trichlorophenoxyacetic acid, but not with the ethylene-producing compound, Ethephon (2-chloroethylphosphonic acid). Hybridization analysis of in-vitro transcription products made in nuclei isolated from untreated and auxin-treated soybean primary leaves and excised hypocotyl sections indicates that, for the two cDNA clones analyzed, the increased RNA levels in auxin-treated organs are at least partially the result of increased transcriptional activity of specific DNA sequences.
TL;DR: A change in the regulation of N- myc expression in neuroblastomas and certain other tumors results in greatly increased expression of each N-myc gene copy.
Abstract: In neuroblastoma lines in which the N-myc gene is present as a single copy, the expression of N-myc as messenger RNA is increased relative to that in nonneuroblastoma cell lines and tumors. The increase of expression in neuroblastomas with amplified N-myc genes is the result of (i) an increase in the absolute amount of expression of each N-myc gene and (ii) an increase in the copy number of the N-myc gene. A second gene--which is amplified in many of the same lines as N-myc--is expressed to about the same degree in most human cell lines and primary tumors regardless of origin (when normalized to gene copy number). Thus, a change in the regulation of N-myc expression in neuroblastomas and certain other tumors results in greatly increased expression of each N-myc gene copy.
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.