Cell cycle dependent genes inducible by different mitogens in cells from different species

CpG methylation prevents YY1-mediated transcriptional activation of the vimentin promoter

Vimentin exhibits a complex pattern of tissue-specific and developmentally regulated expression, but the mechanisms underlying the complex transcriptional regulation remain poorly understood. Here we examined whether vimentin expression can be regulated by CpG methylation of the vimentin promoter. Two subclones of the rat C6 glioma cells were established with (C6vim+) and without (C6vim-) vimentin. Bisulfite genomic sequencing revealed that the vicinity of the transcription start site within the vimentin promoter is highly methylated in C6vim- cells but not in C6vim+ cells. Treatment of C6vim- cells with a demethylating agent, 5-aza-2'-deoxycytidine, restored vimentin expression, indicating that hypermethylation of the promoter region correlates with transcriptional silencing of the vimentin gene. Electrophoretic mobility shift assay (EMSA) and transient transfection experiments demonstrated that YY1 is a key transcriptional activator regulating vimentin expression and that CpG methylation is sufficient to prevent the binding of YY1 to the vimentin promoter. These data suggest that the inability of YY1 to access the hypermethylated promoter may be one of the mechanisms that mediate vimentin downregulation.

TGFbeta1 regulation of vimentin gene expression during differentiation of the C2C12 skeletal myogenic cell line requires Smads, AP-1 and Sp1 family members

Vimentin exhibits a complex pattern of developmental and tissue-specific expression regulated by such growth factors as TGFbeta1, PDGF, FGF, EGF and cytokines. Vimentin is expressed in the more migratory, mesenchymal cell and its expression is often down-regulated to make way for tissue-specific intermediate filaments proteins such as desmin in muscle. Here, we suggest a mechanism to explain how TGFbeta1 contributes to the up-regulation of vimentin expression while blocking myogenesis. TGFbeta1 binds to serine/threonine kinase receptors resulting in the phosphorylation of Smad2 and Smad3, followed by formation of a heteromeric complex with Smad4. The translocation of this complex to the nucleus modulates transcription of selected genes such as vimentin. However, the vimentin gene lacks a consensus TGFbeta1 response element. By transient transfection analysis of vimentin's various promoter elements fused to the CAT reporter gene, we have determined that tandem AP-1 sites surrounded by GC-boxes are required for TGFbeta1 induction. Mutations within this region eliminated the ability of Smad3 to induce reporter gene expression. DNA precipitation and ChIP assays suggest that c-Jun, c-Fos, Smad3 and Sp1/Sp3 interact over this region, but this interaction changes during myogenesis with TGFbeta1 induction.

ZBP-89 represses vimentin gene transcription by interacting with the transcriptional activator, Sp1

Vimentin, a member of the intermediate filament protein family, is regulated both developmentally and tissue specifically. It is also a marker of the metastatic potential of many tumor cells. Pre viously, the human vimentin promoter has been shown to contain multiple elements for the binding of both positive- and negative-acting regulatory factors. Transient transfection analysis of various vimentin 5'-end promoter sequences and mutants thereof fused to a reporter gene further defined two regulatory elements, a positive element that binds Sp1 and a negative element that binds the protein ZBP-89. ZBP-89 has been shown to be either a repressor or an activator of gene expression, depending on the promoter. Here, we show that for vimentin, both ZBP-89 and ZBP-99 repress reporter gene expression in Schneider (S2) cells. Deletion constructs confirm that the glutamine-rich region of Sp1 is required to enhance vimentin transcription, whereas the N-terminus of ZBP-89 is required to interact with Sp1 and repress gene expression. The overexpression of hTAF(II)130 can alleviate ZBP-89 repression in S2 cells, suggesting how ZBP-89 might serve to block gene expression.

Healthy mice with an altered c-myc gene: role of the 3' untranslated region revisited

c-Myc is a protooncogene involved in the control of cellular proliferation, differentiation and apoptosis. Like many other early response genes, regulation of c-myc expression is mainly controlled at the level of mRNA stability. Multiple cis-acting destabilizing elements have been described that are located both in the protein-coding region and in the 3' untranslated region (3' UTR). However, it is not known when they function during development and whether they act as partly redundant or independent elements to regulate c-myc mRNA level of expression. To begin to address these questions, we created a series of c-myc alleles modified in the 3' UTR, using homologous recombination and the Cre/loxP system, and analysed the consequences of these modifications in ES cells and transgenic animals. We found that deletion of the complete 3' UTR, including runs of Us and AU-rich elements proposed, on the basis of cell-culture assays, to be involved in the control of c-myc mRNA stability, did not alter the steady-state level of c-myc mRNA in any of the various situations analysed in vivo. Moreover, mice homozygous for the 3' UTR-deleted gene were perfectly healthy and fertile. Our results therefore strongly suggest that the 3' UTR of c-myc mRNA does not play a major role in the developmental control of c-myc expression.

An antisilencer element is involved in the transcriptional regulation of the human vimentin gene

Vimentin is an intermediate filament protein normally expressed in cells of mesenchymal origin. The promoter of the human vimentin gene was previously reported to contain two positive-acting regions, separated by a negative region (Rittling, S.R., Baserga, R., 1987. Functional analysis and growth factor regulation of the human vimentin promoter. Mol. Cell. Biol. 7, 3908-3915). Here, detailed studies reveal two additional regulatory elements, a new positive transcriptional element located between -717 and -757, and a new repressor element at -780 to -821. In transient transfections, the positive-acting element is able to completely override the effect of different silencer elements when fused to a heterologous promoter. However, this element does not enhance gene activity when the silencer element is absent and thus cannot be viewed as a true enhancer. Since it appears to overcome the effect of a silencer element, we refer to it as an antisilencer element. Gel mobility shift assays, UV-cross-linking experiments, and Southwestern blots reveal that a 105-kDa protein specifically binds to this region.

A 28-bp negative element with multiple factor-binding activity controls expression of the vimentin-encoding gene

The promoter of the human vimentin-encoding gene (VIM) contains two enhancers separated by a negative region. The distal and proximal enhancers bind the transcription factors, AP-1 and NK-kappaB, respectively, which contribute to serum induction of Vim synthesis. We were interested in looking for particular regulatory elements that might be responsible for tissue-specific extinction and culture-dependent activation of human VIM. We have identified a 48-bp sequence in the distal enhancer which had not been reported before. This sequence includes a negative element, NE2, which confers transcriptional repression in transfection experiments and binds at least two factors in vitro. NE2 may participate in the differentiation-stage-specific control of VIM expression which involves multiple regulatory sequences and several positive and negative trans-acting factors.

Two homologous enhancer elements in the chicken vimentin gene may bind a nuclear factor in common with a nearby silencer element

Vimentin, a cytoskeletal protein belonging to the intermediate filament protein family, exhibits a complex pattern of expression. In the case of the chicken vimentin gene, several regulatory elements within the 5' region of the gene have been characterized, including an enhancer activity between -160 and -320, which may contribute to the down-regulation of vimentin expression during myogenesis. In this study, sequences within this region were examined via transient transfections of various deletion constructs, and two distinct enhancer elements were found, one on either side of a previously described silencer element. These two enhancer elements also enhanced transcription when fused separately to the basal promoter region of the chicken vimentin gene. Gel mobility shift assays, UV cross-linking experiments, and DNase I protection studies indicate that these two enhancer elements and the silencer element all contain a common binding site for the previously described 95-kDa silencer element binding protein, suggesting that this regulatory protein can act as both an activator and a repressor.

Immunohistochemical expression of placental alkaline phosphatase and vimentin in epithelial ovarian neoplasms

The immunohistochemical expression of PLAP and vimentin was assessed in 23 benign, 6 borderline malignant and 31 malignant epithelial ovarian neoplasms. PLAP and vimentin were expressed in some benign (3/23 and 5/23 respectively) and borderline malignant (2/6 for both markers) tumours and they were often expressed in malignant tumours (16/31 and 17/31 respectively). There was a significantly increased expression of PLAP and vimentin in serous cystadenomas and serous carcinomas compared to their mucinous counterparts. Although there was no significant correlation between PLAP expression and histologic grade of carcinomas there was a trend towards increased expression in more differentiated carcinomas. No correlation was found between vimentin expression and degree of differentiation.

Identification of a negative element in the human vimentin promoter: modulation by the human T-cell leukemia virus type I Tax protein

The vimentin gene is a member of the intermediate filament multigene family and encodes a protein expressed, in vivo, in all mesenchymal derivatives and, in vitro, in cell types of various origin. We have previously demonstrated that the expression of this growth-regulated gene could be trans activated by the 40-kDa Tax protein of HTLV-I (human T-cell leukemia virus type I) and that responsiveness to this viral protein was mediated by the presence of an NF-kappa B binding site located between -241 and -210 bp upstream of the mRNA cap site (A. Lilienbaum, M. Duc Dodon, C. Alexandre, L. Gazzolo, and D. Paulin, J. Virol. 64:256-263, 1990). These previous assays, performed with deletion mutants of the vimentin promoter linked to the chloramphenicol acetyltransferase gene, also revealed the presence of an upstream negative region between -529 and -241 bp. Interestingly, the inhibitory activity exerted by this negative region was overcome after cotransfection of a Tax-expressing plasmid. In this study, we further characterize the vimentin negative element and define the effect of the Tax protein on the inhibitory activity of this element. We first demonstrate that a 187-bp domain (-424 to -237 bp) behaves as a negative region when placed upstream either of the NF-kappa B binding site of vimentin or of a heterologous enhancer such as that present in the desmin gene promoter. The negative effect can be further assigned to a 32-bp element which is indeed shown to repress the basal or induced activity of the NF-kappa B binding site.(ABSTRACT TRUNCATED AT 250 WORDS)

Identification of a negative element in the human vimentin promoter: modulation by the human T-cell leukemia virus type I Tax protein

The vimentin gene is a member of the intermediate filament multigene family and encodes a protein expressed, in vivo, in all mesenchymal derivatives and, in vitro, in cell types of various origin. We have previously demonstrated that the expression of this growth-regulated gene could be trans activated by the 40-kDa Tax protein of HTLV-I (human T-cell leukemia virus type I) and that responsiveness to this viral protein was mediated by the presence of an NF-kappa B binding site located between -241 and -210 bp upstream of the mRNA cap site (A. Lilienbaum, M. Duc Dodon, C. Alexandre, L. Gazzolo, and D. Paulin, J. Virol. 64:256-263, 1990). These previous assays, performed with deletion mutants of the vimentin promoter linked to the chloramphenicol acetyltransferase gene, also revealed the presence of an upstream negative region between -529 and -241 bp. Interestingly, the inhibitory activity exerted by this negative region was overcome after cotransfection of a Tax-expressing plasmid. In this study, we further characterize the vimentin negative element and define the effect of the Tax protein on the inhibitory activity of this element. We first demonstrate that a 187-bp domain (-424 to -237 bp) behaves as a negative region when placed upstream either of the NF-kappa B binding site of vimentin or of a heterologous enhancer such as that present in the desmin gene promoter. The negative effect can be further assigned to a 32-bp element which is indeed shown to repress the basal or induced activity of the NF-kappa B binding site.(ABSTRACT TRUNCATED AT 250 WORDS)

Growth-regulated expression of vimentin in hamster fibroblasts is a result of increased transcription

We have previously shown that vimentin is a growth-regulated gene whose mRNA levels increase after serum stimulation of quiescent hamster fibroblasts. In this study, the control of the growth-regulated expression of vimentin was determined in ts13 cells induced to proliferate by serum. Both transcriptional and post-transcriptional mechanisms of regulation were examined by determining transcriptional rates, cytoplasmic transcript abundance, transcript stability, and protein abundance. We observed a fourfold increase in vimentin transcripts in the cytoplasm of serum-stimulated ts13 cells. Since transcripts are stable in both quiescent and stimulated cells, this induction of vimentin expression is a result of a fivefold increase in vimentin-specific transcriptional activity. As a result of this increased transcript availability, the abundance of polymerized vimentin protein increased following serum stimulation of quiescent fibroblasts. Overall, the induction of vimentin expression in fibroblasts by serum is a consequence of increased vimentin-specific transcriptional activity. The significance of this with regard to cytoskeletal organization and cell division is discussed.

Expression of growth-regulated genes in normal and SV40 transformed hamster fibroblasts

Transformation by the oncogenic virus SV40 has been shown to alter the expression of cellular genes at the level of RNA abundance. Many of these genes have yet to be identified. We have determined, by Northern blot analysis, the abundance levels of several growth-regulated genes in SV40-transformed cell lines to determine if their expression is altered and correlates with the ability of SV40 transformed cells to grow in low serum containing media. The mRNA abundance levels of the G1-specific genes 2A9/calcyclin, 2F1/translocase, and 4F1/vimentin were determined in the parental hamster fibroblast cell line, tk-ts13, and in two SV40 transformants, HR5 and HR8 cells, grown in medium containing 10% calf serum (normal medium) and in HR5 and HR8 cells adapted to passage in medium containing low serum. A spontaneous transformant of the parental line capable of growth in low serum in the absence of SV40 transformation (tk-ts13/1%), was also included in these studies. The low serum adapted SV40-transformed cells and the spontaneous tk-ts13 transformed cells grew more vigorously than their nonadapted counterparts in medium containing low serum. The low serum adapted cells also grew to higher saturation densities in low serum and to densities comparable to those in high serum, whereas the nonadapted cells grew to low saturation densities in low serum, but not as low as the untransformed parental.(ABSTRACT TRUNCATED AT 250 WORDS)

Wound-factor-induced and cell cycle phase-dependent expression of 9E3/CEF4, the avian gro gene

The gro genes encode for secreted proteins with sequence homologies to inflammatory mediators. Little is known about the function of these proteins or their regulation. The chicken gro (9E3/CEF4) is expressed abundantly in the cells of proliferating cultures but at very low levels in confluent cultures. In vivo, this gene is expressed in connective tissue and overexpressed at sites of injury, especially in areas of neovascularization. Here we provide a bridge between these observations by examining in culture the effect on 9E3 expression and DNA synthesis induced by cell damage and by addition of factors known to be released on wounding. We mimicked wounding by scraping swaths across confluent cultures of embryonic fibroblasts and determined the time dependence of expression of 9E3 mRNA and incorporation of 3H-thymidine. We find that 9E3 is (1) transiently expressed after "wounding" or serum-stimulation; (2) expressed in a cell cycle phase-dependent manner; it is triggered during the G0-G1 transition or early in G1 and subsides during S-phase; and (3) stimulated to high levels by a-fibroblast growth factor (aFGF), bFGF, transforming growth factor alpha (TGF alpha), and TGF beta, to intermediate levels by platelet-derived growth factor and not stimulated by epidermal growth factor. We also find that cells that are constantly cycling do not express 9E3, indicating that they skip either the portion of the cell cycle where 9E3 is induced or that they constitutively express a repressor of transcription or an RNA-degrading enzyme. Taken together, these observations suggest that the product of this gene could play more than one role in vivo. For example, in normal tissues the 9E3 protein could be involved in the exit of cells from the resting stage, whereas during wound healing the secreted protein or its cleavage products also could play a role in angiogenesis.

Growth factor modulation of melanoma growth stimulatory activity mRNA expression in human malignant melanoma cells correlates with cell growth

This report demonstrates that the expression of melanoma growth stimulatory activity (MGSA) mRNA can be modulated in a positive fashion in the Hs294T human melanoma cell line by PDGF and MGSA. There is close correlation between MGSA expression and the pattern of cell growth in Hs294T cells.

AP-1/jun binding sites mediate serum inducibility of the human vimentin promoter

The vimentin gene is inducible by serum in quiescent Balb/c 3T3 cells, but the molecular mechanism of this induction is unknown. The results presented here represent a first step towards the elucidation of the pathway of events leading from growth factor-receptor interaction to this induction. A series of Bal 31 deletions of the human vimentin promoter are used to show that a sequence residing at -700 is responsible for the serum, and also TPA inducibility of this gene. This sequence is able to confer serum inducibility upon uninducible constructs regardless of its position and orientation, indicating that it is this element alone which is required for this induction. The isolated sequence is a strong enhancer as well. Further deletions and the use of synthetic oligonucleotides demonstrate that a 24-mer containing two AP-1/jun binding sites confer both serum and TPA inducibility upon the human vimentin gene. Gel retardation analysis confirms that this sequence binds an AP-1 -like protein.

Patterns of mRNA expression during early cell growth differ in kidney epithelial cells destined to undergo compensatory hypertrophy versus regenerative hyperplasia

An increase in cell size and protein content is characteristic of cells undergoing hypertrophy and of replicating cells prior to DNA synthesis. Cell enlargement in the two situations could be regulated by similar early events with an interruption of the cell cycle occurring in hypertrophy, or the two processes could be uncoupled. In vivo models were used to compare hypertrophy induced by unilateral nephrectomy and hyperplasia induced by folic acid injection in rabbit renal cortical cells. Within 48 hr, cell volume increased in both groups but the number of cells in the cell cycle and DNA synthesis was increased only after folic acid. Patterns of mRNA expression of the following three groups of cell cycle-dependent genes were analyzed: (i) protooncogenes (c-fos, c-myc, and c-Ha-ras), (ii) structural protein genes (vimentin and beta-actin), and (iii) transport protein genes (Na+, K+-ATPase, ADP-ATP translocase, and calcyclin). mRNAs for all genes, except calcyclin and c-Ha-ras, were detected in controls. Folic acid generally induced rapid, transient increases in mRNA levels, but after unilateral nephrectomy, expression of most mRNAs showed a gradual, progressive increase. These data indicate that gene expression in the early stages of cell enlargement differs in cells destined to undergo proliferation vs. hypertrophy. The term "sustained message amplification" is proposed to describe the hypertrophied cell.

Functional analysis and growth factor regulation of the human vimentin promoter

Vimentin is a growth-regulated gene whose mRNA levels increase severalfold after stimulation of quiescent cells. We have isolated and sequenced a genomic fragment of human DNA containing the vimentin 5'-flanking sequence and untranslated region. S1 nuclease analysis was used to determine the transcription initiation site. Deletion mutants of the promoter region were constructed, linked to a chloramphenicol acetyltransferase gene, and analyzed for transient expression by transfection into BALB/c 3T3 cells. These experiments revealed the presence in the human vimentin promoter region of a negative-regulatory element, flanked by positive elements. The most 5' of the positive elements is able to overcome the effects of the negative element. Analysis of these deletion constructs in stable cell lines confirmed the results of the transient assays. Using these stable cell lines, we can also demonstrate that the vimentin promoter region can confer platelet-derived growth factor inducibility to a linked chloramphenicol acetyltransferase gene and that the sequences required for this inducibility reside between positions -241 and +73.

Functional analysis and growth factor regulation of the human vimentin promoter

Vimentin is a growth-regulated gene whose mRNA levels increase severalfold after stimulation of quiescent cells. We have isolated and sequenced a genomic fragment of human DNA containing the vimentin 5'-flanking sequence and untranslated region. S1 nuclease analysis was used to determine the transcription initiation site. Deletion mutants of the promoter region were constructed, linked to a chloramphenicol acetyltransferase gene, and analyzed for transient expression by transfection into BALB/c 3T3 cells. These experiments revealed the presence in the human vimentin promoter region of a negative-regulatory element, flanked by positive elements. The most 5' of the positive elements is able to overcome the effects of the negative element. Analysis of these deletion constructs in stable cell lines confirmed the results of the transient assays. Using these stable cell lines, we can also demonstrate that the vimentin promoter region can confer platelet-derived growth factor inducibility to a linked chloramphenicol acetyltransferase gene and that the sequences required for this inducibility reside between positions -241 and +73.

Expression of growth-associated genes in various tissues of the fetal and adult rat

4F1, 2A9 and 2F1 represent three of a number of cDNA sequences which have been identified because their cognate RNAs markedly increase when quiescent cells in culture are stimulated with serum. Studies using a variety of cell culture systems have shown that the expression of these genes is modulated by various growth factors and mitogens and thus such genes are considered to be 'growth-associated.' Thus far, little information has been obtained with these in vitro systems about the function of these genes. In an attempt to begin to elucidate the role of these genes (if any) in the physiology of the normal cell, we have analyzed the levels of 4F1, 2A9 and 2F1 transcripts in a variety of differentiated organs and tissues of adult and fetal rats. Our results show that each of these growth-associated genes exhibits its own unique pattern of expression, unrelated to the proliferative activity of the tissue. These data suggest that these genes most likely do have specific functions in normal tissue in addition to their role in the induction of DNA synthesis in quiescent cells in culture.

Expression of growth-regulated genes in tsJT60 cells, a temperature-sensitive mutant of the cell cycle

We have investigated the expression of growth-regulated genes in tsJT60 cells, a temperature-sensitive (ts) mutant of Fischer rat cells, which, on the basis of its kinetic behavior, can be classified as a G0 mutant. It grows normally at 34 degrees C and also at 39.5 degrees C if shifted to the higher temperature during exponential growth. However, if the cell population is first made quiescent by serum deprivation, subsequent stimulation by serum induces the cells to enter S phase at 34 degrees C but not at 39.5 degrees C. A panel of growth-regulated genes was used that included three protooncogenes (c-fos, c-myc, and p53), several genes that are induced in G0 cells stimulated by growth factors (beta-actin, 2A9, 2F1, vimentin, JE-3, KC-1, and ornithine decarboxylase), and an S-phase gene (histone H3). The expression of these growth-regulated genes was studied in both tsJT60 cells and its parental cell line, rat 3Y1 cells. All the genes tested, except histone H3, are similarly induced when quiescent tsJT60 cells are stimulated by serum at either permissive or restrictive temperatures. These results raise intriguing questions on the nature of quiescence and the relationship between G0 and G1 in cells in culture.