Spl phosphorylation induced by serum stimulates the human alpha2(I) collagen gene expression.

Serum has been known to stimulate collagen production by dermal fibroblasts. As part of an ongoing study of the molecular mechanisms of collagen production, we have investigated transcriptional regulation of the human alpha2(I) collagen gene by serum in human dermal fibroblasts. Serum responsive elements were mapped by deletion analysis between bp -353 and -264, and between -148 and -108 in the alpha2(I) collagen promoter. Further functional analysis of the alpha2(I) collagen promoter containing various substitution mutations revealed that serum stimulation of this promoter is mediated equally by a GC-rich region located between bp -303 and -271 and by the TCCTCC motif located between bp -123 and -128, both of which constitute binding sites for transcription factor Spl and Sp3. No differences were observed in electrophoretic mobility shift assays between unstimulated and serum stimulated fibroblasts. The Spl inhibitor mithramycin blocked stimulation of the alpha2(I) collagen promoter activity by serum. Furthermore, immunoprecipitation analysis showed that serum stimulation increased Spl phosphorylation. In conclusion, this study characterized response elements that mediate serum stimulation of the human alpha2(I) collagen promoter and suggests that serum stimulation was mediated via Sp1/Sp3 binding sites in this promoter.