ONCOSTATIN-M STIMULATES TRANSCRIPTION OF THE HUMAN ALPHA-2(I) COLLAGEN GENE VIA THE SP1 SP3-BINDING SITE/

Oncostatin M (OSM), a member of the hematopoietic cytokine family, has been implicated in excessive bone growth and in the process of fibros is, As part of an ongoing study of the molecular mechanisms of fibrosi s, we have investigated the transcriptional regulation of the alpha 2( I) collagen gene by OSM in human fibroblasts, An OSM response element was mapped by deletional analysis between base pairs (bp) -148 and -10 8 in the alpha(I) collagen promoter, Further functional analysis of th e alpha 2(I) collagen promoter containing various substitution mutatio ns revealed that both the basal activity and OSM stimulation of this p romoter are mediated by a TCCTCC motif located between bp -128 and -12 3. Futhermore, three copies of the 12-bp synthetic alpha 2(I) collagen promoter fragment containing the ''TCC'' motif conferred OSM inducibi lity to the otherwise unresponsive thymidine kinase promoter, Electrop horetic mobility shift assays demonstrated that the TCCTCC motif const itutes a novel binding site far the transcription factors Spl and Sp3. No differences have been observed in in vitro gel shift binding assay s between unstimulated and OSM-stimulated fibroblasts, However, subtle conformational changes were detected in the region of the promoter su rrounding TCC repeats after OSM stimulation using in vivo footprint an alysis. In conclusion, this study characterized a dual-function respon se element that mediates the basal activity and OSM stimulation of the human alpha 2(I) collagen promoter.