Cloning and characterization of a transcription factor that binds to the proximal promoters of the two mouse type I collagen genes.

We have used the yeast one-hybrid system to clone transcription factors that bind to specific sequences in the proximal promoters of the type I collagen genes. We utilized as bait the sequence between -180 and -136 in the pro-alpha2(I) collagen promoter because it acts as a functional promoter element and binds several DNA-binding proteins. Three cDNA clones were isolated that encoded portions of the mouse SPR2 transcription factor, whereas a fourth cDNA contained a potential open reading frame for a polypeptide of 775 amino acids and was designated BFCOL1. Recombinant BFCOL1 was shown to bind to the -180 to -152 segment of the mouse pro-alpha2(I) collagen proximal promoter and to two discrete sites in the proximal promoter of the mouse pro-alpha1(I) gene. The N-terminal portion of BFCOL1 contains its DNA-binding domain. DNA transfection experiments using fusion polypeptides with the yeast GAL4 DNA-binding segment indicated that the C-terminal part of BFCOL1 contained a potential transcriptional activation domain. We speculate that BFCOL1 participates in the transcriptional control of the two type I collagen genes.