Presence of a regulatory element within the first intron of the human platelet-derived growth factor-A chain gene.

We detected a suppressive element in the first intron of the human platelet-derived growth factor A chain (PDGF-A) gene. Two or more proteins, at least 110-kd and 90-kd proteins, were bound over a wide region of this fragment, and the fragment suppressed the expression of the PDGF-A chain via these proteins in vivo. Since the fragment also had suppressor activity on the promoter of the PDGF-B chain, it may be involved in a suppressive mechanism of gene expression common to PDGF-A and -B chains. Four tandem repeats of CCCCAT(CCCC) and three direct repeats of GGGGAG were observed in this region. The expression of the PDGF-A chain is considered to be regulated by a mechanism involving not only the 5' upstream region but also introns.