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Alpha2(I) collagen gene regulation by protein kinase C signaling in human dermal fibroblasts.

ABSTRACT: We investigated the mechanisms by which protein kinase C (PKC) regulates the expression of the alpha2(I) collagen gene in normal dermal fibroblasts. Reduction of PKC-alpha activity by treatment with Gö697-6 or by overexpression of a dominant negative (DN) mutant form decreased alpha2(I) collagen gene expression. This decrease required a sequence element in the collagen promoter that contains Sp1/Sp3 binding sites. Reduction of PKC-delta activity by rottlerin or overexpression of DN PKC-delta also decreased alpha2(I) collagen gene expression. This effect required a separate sequence element containing Sp1/Sp3-binding sites and an Ets-binding site. In both cases, point mutations within the response elements abrogated the response to PKC inhibition. Forced overexpression of Sp1 rescued the PKC inhibitor-mediated reduction in collagen protein expression. A DNA affinity precipitation assay revealed that inhibition of PKC-delta by rottlerin increased the binding activity of endogenous Fli1 and decreased that of Ets1. On the other hand, TGF-beta1, which increased the expression of PKC-delta, had the opposite effect, increasing the binding activity of Ets1 and decreasing that of Fli1. Our results suggest that PKC-delta is involved in the regulation of the alpha2(I) collagen gene in the presence or absence of TGF-beta. Alteration of the balance of Ets1 and Fli1 may be a novel mechanism regulating alpha2(I) collagen expression.

SUBMITTER: Jinnin M

PROVIDER: S-EPMC552962 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:AIM:To clarify the fractional activity of promoters from human alpha1(I) procollagen gene, the interaction between cis-elements and consensus DNA-binding proteins responsible for high promoter activity, and the potential application of promoter competitors as well as cytokines for antifibrogenesis. METHODS:Sequence between 2483 bp upstream of the start of transcription and 42 bp downstream of this site was investigated with serial 5'-deletion. The 5'-deleted promoters recombined with chloramphenicol acetyltransferase (CAT) as reporter gene were transiently transfected to human dermal fibroblasts. Electrophoretic mobility shift assay was performed to show the DNA-protein binding capacity of the promoter sequence. Cytokines including tumor necrosis factor alpha (TNFalpha) and interferons (INFs) were added to the culture medium of transiently transfected fibroblasts. Competitor DNA for the binding sites of Sp-1, Ap-1 and NF-1 was individually cotransfected transiently in order to block the promoter-driven CAT expression. RESULTS:Sequences of -2483 to +42 bp and -268 to +42 bp of human alpha1(I) procollagen gene had high activity as promoters. Binding sites for Ap-1 and Sp-1 were among the cis-regulatory elements recognizing consensus transcription factors responsible for basal promoter activity of sequence -268 to +42 bp. TNFalpha, IFNalpha, IFNbeta showed inhibitory effects on sequence -2 483 to +42 bp as promoter with activities 43%, 62% and 60% of control respectively. Transfection of the promoter competitors could reverse the promoter activity of -268 to +42 bp 40-60%. CONCLUSION:Sequences of -2 483 to +42 bp recombined with reporter gene provide an ideal construction for transcriptional study of alpha1(I) procollagen gene. The anti-collagen capacity of TNFalpha and IFNs is associated with their transcriptional regulation. Ap-1 and Sp-1 mediate the basal transcriptional activation of human alpha1(I) procollagen gene in dermal fibroblasts. Competitors for highly active promoters might be a novel potential candidate in fibrotic blockade.

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Alpha2(I) collagen gene regulation by protein kinase C signaling in human dermal fibroblasts.

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