Coordinate transcriptional regulation of type I procollagen genes by Rous sarcoma virus

Effect of erythromycin A and its new derivative EM201 on type I collagen production by cultured dermal fibroblasts

Thinning of the dermis is the principal histological change in atrophic skin disorders and aged skin. It is caused due to a decreased amount of collagen in the dermis. Macrolides have been reported to exert various pharmacological activities, including anti-inflammatory activity, tumor angiogenesis inhibition and growth inhibition of fibroblasts, in addition to antimicrobial activity. In this study, we investigated the effects of erythromycin A (EMA) and its new derivative EM201 on type I collagen production by cultured dermal fibroblasts. Dermal fibroblasts were cultured with 10(-9) M-10(-5) M EMA or EM201, and collagen production was measured by incubation with radioactive proline, SDS-polyacrylamide gel electrophoresis and fluorography. mRNA levels were measured by Northern blots analysis, and to investigate transcriptional levels luciferase assays were also performed. The results showed that both EMA and EM201 increased collagen production and type I collagen mRNA level (to a maximum of 200% with EMA and 250% with EM201) in a dose-dependent manner in cultured dermal fibroblasts. Transcription of the type I collagen gene was also increased by both macrolides. These results suggest that EMA and EM201 have the potential to improve the thinning of the dermis in atrophic skin disorders and aged skin.

Structural and functional studies on the interstitial collagen genes

An understanding of the molecular mechanisms which control expression of the type I and III collagen genes may provide a rational basis for the design of more effective therapeutic approaches to fibrotic diseases. The structure of the interstitial collagen genes is reviewed and potential sites which could control their expression are examined. One approach to the study of the regulation of these genes consists in DNA-mediated gene transfection experiments and is discussed in this paper.

EM703, the new derivative of erythromycin, inhibits transcription of type I collagen in normal and scleroderma fibroblasts

BACKGROUND

Excessive accumulation of collagen in the skin and internal organs in systemic sclerosis (SSc) is considered to result from enhanced transcription of collagen in fibroblasts. Macrolides have been reported to show various pharmacological activities. Recently, it was reported that EM703, a new derivative of erythromycin, improved bleomycin-induced pulmonary fibrosis in mice.

OBJECTIVE

Therefore, we attempted to examine the effects of EM703 on the type I collagen synthetic activity in normal and SSc dermal fibroblasts.

METHODS

Normal and SSc dermal fibroblasts were cultured with various concentrations of Erythromycin A or EM703 for 48h. Amount of type I collagen in the culture medium was measured with ELISA with anti-type I collagen antibody. Type I collagen mRNA levels were measured by northern blots analysis and type I collagen transcription and regulation of the human COL1A1 promoter activity were examined by transient transfection and luciferase assay. Electrophoretic gel mobility shift assay was also performed for measurement of binding activities of DNA binding factors to the COL1A1 promoter.

RESULTS

We found that EM703 reduced collagen production and the mRNA levels of alpha1(I) collagen in a dose-dependent manner in the normal fibroblasts. The transcription of COL1A1 was downregulated as detected by the luciferase assay. The downregulation was also detected using DNA containing various short lengths of the COL1A1 promoter region. EM703 did not inhibit COL1A1 transcription when the luciferase assay was performed using DNA containing the COL1A1 promoter with a short substitution mutation of the CCAAT box. Decreased production of type I collagen at the transcriptional level was also found in SSc fibroblasts treated with EM703.

CONCLUSION

These results suggest that EM703 inhibits the transcription of type I collagen in both normal and SSc fibroblasts, and that the transcription is inhibited through the CCAAT box of the COL1A1 promoter.

Identification of novel TGF-beta /Smad gene targets in dermal fibroblasts using a combined cDNA microarray/promoter transactivation approach

Despite major advances in the understanding of the intimate mechanisms of transforming growth factor-beta (TGF-beta) signaling through the Smad pathway, little progress has been made in the identification of direct target genes. In this report, using cDNA microarrays, we have focussed our attention on the characterization of extracellular matrix-related genes rapidly induced by TGF-beta in human dermal fibroblasts and attempted to identify the ones whose up-regulation by TGF-beta is Smad-mediated. For a gene to qualify as a direct Smad target, we postulated that it had to meet the following criteria: (1) rapid (30 min) and significant (at least 2-fold) elevation of steady-state mRNA levels upon TGF-beta stimulation, (2) activation of the promoter by both exogenous TGF-beta and co-transfected Smad3 expression vector, (3) up-regulation of promoter activity by TGF-beta blocked by both dominant-negative Smad3 and inhibitory Smad7 expression vectors, and (4) promoter transactivation by TGF-beta not possible in Smad3(-/-) mouse embryo fibroblasts. Using this stringent approach, we have identified COL1A2, COL3A1, COL6A1, COL6A3, and tissue inhibitor of metalloproteases-1 as definite TGF-beta/Smad3 targets. Extrapolation of this approach to other extracellular matrix-related gene promoters also identified COL1A1 and COL5A2, but not COL6A2, as novel Smad targets. Together, these results represent a significant step toward the identification of novel, early-induced Smad-dependent TGF-beta target genes in fibroblasts.

Tracking COL1A1 RNA in osteogenesis imperfecta. splice-defective transcripts initiate transport from the gene but are retained within the SC35 domain

This study illuminates the intra-nuclear fate of COL1A1 RNA in osteogenesis imperfecta (OI) Type I. Patient fibroblasts were shown to carry a heterozygous defect in splicing of intron 26, blocking mRNA export. Both the normal and mutant allele associated with a nuclear RNA track, a localized accumulation of posttranscriptional RNA emanating to one side of the gene. Both tracks had slightly elongated or globular morphology, but mutant tracks were cytologically distinct in that they lacked the normal polar distribution of intron 26. Normal COL1A1 RNA tracks distribute throughout an SC-35 domain, from the gene at the periphery. Normally, almost all 50 COL1A1 introns are spliced at or adjacent to the gene, before mRNA transits thru the domain. Normal COL1A1 transcripts may undergo maturation needed for export within the domain such as removal of a slow-splicing intron (shown for intron 24), after which they may disperse. Splice-defective transcripts still distribute thru the SC-35 domain, moving approximately 1-3 micrometer from the gene. However, microfluorimetric analyses demonstrate mutant transcripts accumulate to abnormal levels within the track and domain. Hence, mutant transcripts initiate transport from the gene, but are impeded in exit from the SC-35 domain. This identifies a previously undefined step in mRNA export, involving movement through an SC-35 domain. A model is presented in which maturation and release for export of COL1A1 mRNA is linked to rapid cycling of metabolic complexes within the splicing factor domain, adjacent to the gene. This paradigm may apply to SC-35 domains more generally, which we suggest may be nucleated at sites of high demand and comprise factors being actively used to facilitate expression of associated loci.

Expression of the neomycin-resistance (neo) gene induces alterations in gene expression and metabolism

The amino 3'-glycosyl phosphotransferase (neo) gene is the selectable marker most widely used in stable transfection or infection protocols. Because the neo gene product has phosphotransferase activity, it might modify the phosphorylation state when introduced in mammalian cells. NIH-3T3 fibroblast cells expressing the neo gene, after either infection with retroviral vectors or transfection with plasmids, showed a 50% reduction in both fructose 2,6-bisphosphate (Fru 2,6-P2) concentration and lactate production compared with control NIH-3T3 cells, indicating that these neo-expressing cells are less glycolytic. In addition, a marked decrease in the levels of mRNA for the procollagen 1 alpha and fibronectin genes was also observed in neo-expressing NIH-3T3 cells. This decrease was concomitant with an increase in the mRNA concentration of the endogenous c-myc gene. FTO-2B rat hepatoma cells also showed modifications in gene expression when the neo gene was introduced by stable transfection or infection. In these cells an increase in both P-enolpyruvate carboxykinase (PEPCK) and tyrosine aminotransferase (TAT) mRNA was observed. These results suggest that neo gene expression may induce changes in the cells, which should be considered when neo-selected cells are used to deliver specific genes in different therapy approaches and in embryo manipulation.

Expression of alpha 2 type I collagen in W8 cells increases cell adhesion and decreases colony formation in soft agar

A chemically transformed cell line, W8, produces alpha 1(I) homotrimers with no alpha 2(I) chains whereas the parent cell line, K16, produces heterotrimers. When W8 cells were transfected with plasmid constructs containing the full length human alpha 2(I) cDNA driven by viral promoters, the cells expressed alpha 2(I) collagen chains forming varying amounts of heterotrimers. Previously, we have shown that K16 and W8 cells have different growth characteristics (Smith, B.D. et al., Cancer Research 43: 4275-4282, 1983) including population doubling, saturation density, cell adhesion and colony formation in soft agar. These parameters were tested for each transfected cell line in order to determine if the alpha 2(I) expression and heterotrimer formation alters cell characteristics. The cells expressing alpha 2(I) forming heterotrimers needed higher concentrations of trypsin or longer time periods to lift from the plate suggesting a role for alpha 2(I) in cell adhesion. The W8 cells formed colonies in soft agar exhibiting anchorage independent growth. However, W8 cells expressing alpha 2(I) chains formed less colonies in soft agar than W8 cells or W8 cells transfected with a neomycin resistant gene indicating that the alpha 2(I) producing cells were less anchorage independent than W8 cells. Population doubling time, morphology and saturation densities were similar to W8 cells with small alterations towards an epithelial morphology. These results demonstrated that alpha 2(I) within heterotrimer is important for cell adhesion and anchorage independent growth.

Purification of a novel factor which binds to the mouse alpha 2 (I) collagen promoter

We have identified and purified a DNA binding protein which specifically binds to a segment of the mouse alpha 2 (I) collagen promoter between -420 and -399 bp upstream of the start of transcription. Purification included heparin-agarose and sequence-specific DNA-affinity chromatography, followed by SDS-PAGE and renaturation of the DNA binding activity after elution from SDS-polyacrylamide gel. The DNA binding activity resides in two species of 42 kDa and 40 kDa, respectively. The levels of DNA binding activity of this factor, which has been tentatively designated as ColF1, are considerably higher in nuclear extracts of NIH-3T3 fibroblasts than in nuclear extracts from epidermal cells, lymphoid cells and transformed NIH-3T3 fibroblasts.

Purification and characterization of collagens from rat fibrosarcoma induced by 3-methylcholanthrene

The distribution of various collagen types was studied in rat fibrosarcoma. Collagens extracted from fibrosarcoma tissue were characterized by the criteria of solubility in NaCl, SDS-PAGE, ion exchange chromatography, CNBr peptide mapping and amino acid analysis. Fibrosarcoma was found to produce excess amount of type V, type I trimer and type III collagens; comparatively, type I collagen and total collagen content were noticed to decrease in fibrosarcoma. We observe that the increase in type V collagen content in fibrosarcoma might be due to the enhanced transcription of type V collagen gene. Increased type I trimer collagen in fibrosarcoma might be attributed to the differential expression of alpha 1(I) and alpha 2(I) gene and might also be due to the expression of a different gene for type I trimer collagen.

Post-transcriptional regulation of the pro alpha 1(I) collagen gene in pro alpha 1(I)-deficient, chemically transformed Syrian hamster embryo fibroblasts

4-Nitroquinoline-1-oxide-transformed Syrian hamster embryo fibroblasts (NQT-SHE) synthesize the pro alpha 2 chain but not the pro alpha 1 subunit of type I procollagen, and they contain little pro alpha 1(I)mRNA. This study shows that there was no accumulation of pro alpha 1(I) poly(A)+ mRNA in NQT-SHE fibroblasts. BHK cells, a normal established line of hamster fibroblasts that synthesized collagen at approximately the same rate as NQT-SHE fibroblasts, nevertheless produced both subunits of type I collagen and contained pro alpha 1(I)mRNA. Run-off transcription assays with isolated nuclei showed that both the pro alpha 1(I) and pro alpha 2(I) genes were transcribed at about the same rate in NQT-SHE cells as well as in the normal BHK cells. These results suggest that a post-transcriptional defect, probably resulting from transformation, prevents the accumulation of pro alpha 1(I)mRNA in NQT-SHE cells.

Constitutive expression of c-fos gene inhibits type 1 collagen synthesis in transfected osteoblasts

To clarify the contribution of c-fos DNA to bone formation, the effect of constitutive expression of the c-fos gene in collagen synthesis was examined by introducing c-fos DNA into osteoblastic MC3T3-E1 cells. The [3H] proline incorporation into the collagenase digestible protein(CDP) and the percent collagen synthesis were significantly decreased in the c-fos transfectants which constitutively express c-fos mRNA as compared with control transfectants. Transcription of type 1(alpha 1) collagen gene was also specifically decreased in the c-fos transfectants. This indicates that constitutive expression of c-fos DNA interferes with bone formation by inhibiting collagen synthesis in osteoblasts.

Reduced levels of alpha 1 (I) collagen mRNA in cells immortalized by mutant p53 or transformed by ras

Genes whose expression patterns are altered in a cell line immortalized by mutant p53 were isolated by differential screening of a cDNA library. Levels of alpha 1 (I) collagen mRNA were reduced in the majority of immortalized cell lines which greatly overproduced the transfected mutant p53. This may reflect a co-selection during the establishment of the cell lines, rather than a direct effect of p53 on alpha 1 (I) collagen gene expression. On the other hand, a more direct relationship could be demonstrated between the expression of activated ras and a reduction in alpha 1 (I) collagen mRNA. Such reduction could partially account for the effects of ras on cell shape and cell proliferation.

Regulation of collagen gene expression by transformed human fibroblasts: decreased type I and type III collagen RNA transcription

The regulation of collagen gene expression in normal diploid human fetal fibroblasts (KMS-6 cells), and fibroblasts immortally transformed by treatment of KMS-6 with Co-60 gamma rays (KMST-6 cells) was compared to that of ones tumorigenically transformed by treatment of KMST-6 cells with Harvey murine sarcoma virus (KMST-6-Ras cells). Synthesized collagenous protein decreased to approximately 30% of that of normal fetal fibroblasts in both transformed cell lines, and the relative rate of collagen synthesis to total protein synthesis decreased about sixfold in KMST-6 cells and twelvefold in KMST-6-Ras cells. The m-RNA levels of type I collagen in both of these cell lines decreased to approximately 20% of that of the control fibroblasts, whereas type III collagen m-RNA levels decreased to only 9% of that of the control. The copy number of the collagen gene in both transformed cell lines was unaltered. The transcriptional rates of collagen alpha 1(I) and collagen alpha 1(III) in both cell lines decreased to 20% and 7% respectively of that of control. These data indicate that collagen synthesis was reduced at the transcriptional level in these transformed human fibroblasts.

The accumulation of type I collagen mRNAs in human embryonic lung fibroblasts stimulated by transforming growth factor-beta

We examined the expression of type I collagen mRNAs (alpha 1(I) and alpha 2 (I)) by embryonic lung fibroblasts in cultures treated with transforming growth factor-beta (TGF-beta). TGF-beta caused a concentration dependent increase in the expression of alpha 1(I) mRNA for type I collagen. TGF-beta at low concentration (0.1 ng/ml) slightly increased the level of alpha 1(I) mRNA. Higher concentrations of TGF-beta (1.0 and 5.0 ng/ml) further increased the amount of alpha 1(I) mRNA. The increase in alpha 1(I) mRNA was associated with a marked increase in production of intact type I collagen molecules. TGF-beta did not increase expression of alpha 2(I) mRNA. The alpha 2(I) mRNA levels in human lung fibroblast cultures were not affected by varying the duration of exposure to TGF-beta nor the concentration of TGF-beta. In contrast, TGF-beta increased the amount of both alpha 1(I) and alpha 2(I) mRNA in NIH3T3 cells. These data suggest that the amount of alpha 2(I) mRNA is not rate limiting with respect to type I collagen production during TGF-beta stimulation in human lung fibroblast cultures.

Prostaglandin D2 receptor of mastocytoma P-815 cells--possible regulation by phosphorylation and dephosphorylation

The 3H-labeled prostaglandin D2 [( 3H]PGD2) binding protein in the membrane fraction of mastocytoma P-815 cells was characterized. The specific binding of [3H]PGD2 to the cells or the membranes reached a maximum at pH 5.6, and was saturable, displaceable and of high affinity when incubated at 0 or 37 degrees C. The Bmax values for [3H]PGD2 binding in the two preparations at pH 5.6 were much higher at 0 degrees C than at 37 degrees C, whereas the Kd values were almost equal (85.3 nM for the cells and 80.5 nM for the membranes, respectively). High specific [3H]PGD2 binding activity in the mildly acid-treated cells was still observed when the external pH was raised from 5.6 to 7.2. Furthermore, specific [3H]PGD2 binding to the membranes (at 0 degrees C, pH 5.6) increased on addition of phosphatase inhibitors (NaF and molybdate) in the presence of 10 microM ATP, but practically disappeared on pretreatment of the membranes with phosphatase. On incubation of the membrane with [gamma-32P]ATP and molybdate, the stimulated incorporation of the [32P]phosphate into several peptides, including ones having an Mr of around 100,000-120,000, was observed. These results suggest that [3H]PGD2 binding in the mastocytoma P-815 cell membrane is controlled through phosphorylation-dephosphorylation of the receptor itself.

Transcription of human type I collagen genes. Variation in the relative rates of transcription of the pro alpha 1 and pro alpha 2 genes

The relative rates of transcription of the two genes for type I collagen have been measured in a runoff transcription assay using nuclei isolated from cultured human fibroblasts. Control experiments indicated that the ratio of pro alpha 1(I)/pro alpha 2(I) transcripts detected with a given nuclear preparation did not vary over a range of transcription times, nuclei concentrations, and amounts of filter-bound cDNA used in the assay. However, a significant difference in the ratio was observed when nuclei isolated from cells grown under different conditions were used. Nuclei from sub-confluent cultures generally transcribed the two genes in a ratio of 2:1 or lower, while nuclei from post-confluent cultures transcribed the genes in a much higher ratio of about 4:1. Analysis of the amount of pro alpha 1(I) and pro alpha 2(I) RNA transcribed suggests that it is the transcription of the pro alpha 1(I) gene, and not the pro alpha 2(I) gene, that varies with culture conditions. The steady state ratios of pro alpha 1(I)/pro alpha 2(I) RNA remained near 2:1 under all conditions. Thus, some post-transcriptional mechanism apparently results in maintenance of the steady-state pro alpha 1(I)/pro alpha 2(I) RNA ratios at approximately 2:1.

Types I and IV procollagen gene expression in cultured rat hepatocytes

The molecular mechanism involved in the expression of collagens by hepatocytes were investigated in both pure and co-culture with another rat liver epithelial cell type (RLEC). We measured the steady-state levels of mRNAs coding for pro alpha 1(I) and pro alpha 1(IV) chains by Northern analysis and by dot blotting, using specific recombinant cDNA probes. In freshly isolated hepatocytes, only small amounts of pro alpha 1(I) and pro alpha 1(IV) mRNAs were detected by dot-blot analysis. After 3 days in culture, the pro alpha 1(I) and pro alpha 1(IV) mRNA levels increased 2 to 5 times. The amount of pro alpha 1(IV) mRNAs was identical in hepatocyte cultured with RLECs while the pro alpha 1(I) mRNA level was 5 times that in pure hepatocyte culture. Hydrocortisone reduced pro alpha 1(I) mRNA in hepatocyte cultures, but had no effect on co-cultured cells. In both culture systems, this glucocorticoid did not act on the steady-state pro alpha 1(IV) mRNA level. Whatever the age and the type of culture (pure or mixed) RLECs exhibited the highest levels of pro alpha 1(I) and pro alpha 1(IV) mRNAs, which were reduced by hydrocortisone. These results show that procollagen gene expression by hepatocytes is not directly correlated with their functional state and that corticosteroids differently affect the expression of different collagen genes and collagen deposition.

Elevated pro alpha 2(I) collagen mRNA levels in cultured scleroderma fibroblasts result from an increased transcription rate of the corresponding gene

Fibroblasts cultured from affected and unaffected skin sites of three scleroderma patients were studied for the activation of type I collagen gene expression. Dot blot hybridizations with pro alpha 2(I) collagen specific cDNA probe revealed 2.9-4.8-fold increases in pro alpha 2(I) mRNA levels in the affected fibroblasts over the unaffected control cells. Transcription rate of the pro alpha 2(I) gene in the nuclei isolated from the same cells was 2.0-3.7-fold higher in the scleroderma fibroblasts than in the controls. The results show that scleroderma fibroblasts have undergone activation of collagen gene expression at the transcriptional level, which subsequently results in elevated procollagen mRNA levels, overproduction of collagen, and development of dermal fibrosis.

Development of molecular hybridization technology to evaluate albumin and procollagen mRNA content in baboons and man

We have developed the methodology for evaluating the effects of pathophysiological conditions on the molecular mechanisms of hepatic protein synthesis and fibrogenesis in baboons and man. Total RNA was extracted from percutaneous liver biopsies of five baboons who were chronically fed an ethanol-rich liquid diet, their pair-fed controls and from humans with a variety of liver abnormalities. Chronic alcohol administration in baboons with liver fibrosis and normal serum albumin levels increased in vitro protein synthesis as measured by [35S]methionine incorporation, albumin mRNA content and Type I procollagen mRNA content. There was no difference in the beta-actin (a constitutive protein) mRNA content. In humans, serum albumin levels correlated with albumin mRNA content as indicated by the intensity of dot blot hybridization and Type I procollagen mRNA levels correlated with the activity of liver fibrosis. The use of RNA-DNA hybridization to investigate procollagen mRNA from human biopsies appears to be a valuable tool for evaluating the potential for collagen synthesis and the future course of liver disease. Besides the use of RNA-DNA hybridization, we describe other methodologies which are useful in delineating the levels of gene expression responsible for hepatic mRNA regulation in normal liver and disease states in man. The use of molecular techniques to evaluate human liver disease provides an opportunity to develop clinically relevant information while at the same time offering the additional advantage of providing fundamental knowledge about fibrogenesis.

Construction and characterization of cDNA clones encoding the 5' end of the chicken pro alpha 1(I) collagen mRNA

As a first step in isolating the 5' end of the chicken pro alpha 1(I) collagen gene, we constructed cDNA clones complementary to the 5' end of the pro alpha 1(I) mRNA using synthetic oligodeoxynucleotides complementary to a conserved region within the N-terminal telopeptide as primers. cDNA clones corresponding to the 5'-untranslated region, signal peptide, N-propeptide and telopeptide were identified based on homology with the human pro alpha 1(I) collagen protein sequence, and on hybridization to pro alpha 1(I) mRNA on Northern blots. A comparison of the nucleotide sequence of these clones with the sequence of the 5' end of the pro alpha 2(I) collagen mRNA confirms that there is 84% homology in a 49-bp region surrounding the translation start point, and shows that there is 70% homology in the nucleotide sequences encoding the N-propeptide triple helical region of the two type-I collagen chains.

Expression of extracellular matrix genes in relation to myogenesis and neoplastic transformation

Fibronectin and alpha 1(I) and alpha 2(I) collagen proteins and RNAs are highly expressed during the growth phase of the non-transformed L6 alpha 1 rat myoblasts. When L6 alpha 1 cells from myotubes following transfer to low serum medium, the levels of fibronectin RNA decrease 8-fold, those of both alpha 2(I) transcripts decrease only 2-fold, while those of both alpha 1(I) transcripts remain stable. The L6 alpha 1 cell-derived non-differentiable low-malignant M4 cell and high-malignant RMS4 cell display only one size of alpha 1(I) and alpha 2(I) transcripts. Compared with L6 alpha 1 myoblasts, the levels of fibronectin and alpha 1(I) RNAs are reduced by factors of 4-5 and 9-10 respectively in both M4 and RMS4 and those of alpha 2(I) RNAs by factors of 10-11 and 20-22 in M4 and RMS4, respectively. Transcription rates are similarly decreased for fibronectin RNA, but are decreased less for collagen RNAs.

Regulation of type I collagen mRNA levels in fibroblasts

Type I procollagen mRNA levels, as well as total RNA and poly(A)-rich mRNA, remain constant when rapidly growing human fetal lung fibroblasts (HFL-1 cells) are compared with quiescent cells. Polysome profiles of cells in both growth states revealed that the distribution of type I collagen mRNA in the mRNP fraction and in polysomes also remained constant even though total RNA and poly(A)-rich mRNA were shifted from polysomes to the mRNP pool in resting cells. Similar results were obtained when RNA fractions in polysomes associated with the cytoskeletal framework were examined. It is known that procollagen production is unaffected by the growth state of cells [Breul, S. D., Bradley, K. H., Hance, A. J., Schafer, M. P., Berg, R. A. and Crystal, R. G. (1980) J. Biol. Chem. 255, 5250-5260] although total protein synthesis is markedly decreased in resting cells. It would therefore appear that the translational control responsible for reduced synthesis of non-collagenous proteins in resting cells does not extend to procollagen and that transcriptional control can account for levels of type I procollagen produced by cultured human fibroblasts.

V-fos stimulates expression of the alpha 1(III) collagen gene in NIH 3T3 cells

NIH 3T3 cells that are transformed by the v-fos containing FBR proviral DNA show a selective increase in alpha 1 (III) collagen synthesis, increased levels of alpha 1(III) collagen RNA and an increased synthesis of this RNA.