chk-YB-1b, a Y-box binding protein activates transcription from rat α1(I) procollagen gene promoter

Type-I collagen, the predominant component of extracellular matrix, is a triple-helical protein consisting of two alpha 1 polypeptides and one alpha 2 polypeptide. Expression of alpha 1 and alpha 2 procollagen genes is co-ordinately regulated under both normal and various pathological conditions. However, the basis of this co-ordinate regulation is not well known. YB-lb, a Y-box protein, has been shown to bind to the polypyrimidine tract present in the alpha 2 procollagen gene. Here, we show that chk-YB-1b, a YB-I homologue, binds in a single-strand-sequence-specific manner to the highly conserved pyrimidine-rich sequences in both alpha 1(I) and alpha 2(I) procollagen promoters from different species, as demonstrated by electrophoretic-mobility-shift assays and by DNaseI footprinting experiments. Transiently transfected and retrovirally expressed antisense oligonucleotides directed against chk-YB-1b specifically inhibited the alpha 1(I) procollagen promoter-driven transcription in cultured fibroblasts. Considering these data and the fact that the chk-YB-1b binding site is one of the few sites between alpha 1(I) and alpha 2(I) procollagen promoters that is conserved from chicken to human, it is proposed that chk-YB-1b may be involved in co-ordinate expression of these two collagen genes.