B-Myb expression in vascular smooth muscle cells occurs in a cell cycle-dependent fashion and down-regulates promoter activity of type I collagen genes.
The members of the Myb family of transcription factors are defined by homology in the DNA-binding domain; all bind the Myb-binding site (MBS) sequence (YG(A/G)C(A/C/G)GTT(G/A)). Here we report that cultured bovine vascular smooth muscle cells (SMCs) express B-myb. Levels of B-myb RNA found in exponential growth were reduced dramatically in serum-deprived quiescent SMCs; B-myb mRNA levels increased in the cell cycle during the late G1 to S phase transition following restimulation with serum, epidermal growth factor, or phorbol ester plus insulin-like growth factor-1. Changes in the rate of B-myb gene transcription could account for part of the observed increase following serum addition. Treatment of SMC cultures with actinomycin D indicated a >4-h half-life for B-myb mRNA during the S phase of the cell cycle. Cotransfection of either a bovine or human B-myb expression vector down-regulated the activity of a multimerized MBS element-driven reporter construct in SMCs. Putative MBS elements were detected upstream of the promoters of the two chains of type I collagen, which we have found to be expressed inversely with growth state of the SMC (Kindy, M. S., Chang, C.-J., and Sonenshein, G. E. (1988) J. Biol. Chem. 263, 11426-11430). In cotransfection experiments, B-myb expression down-regulated the promoter activity of alpha1(I) and alpha2(I) collagen constructs an average of 92 and 82%, respectively. Thus, B-myb represents a potential link in the observed inverse relationship between collagen gene expression and growth of vascular SMCs.
Marhamati
D J
DJ
Department of Biochemistry, Boston University School of Medicine, Boston, Massachusetts 02118, USA.
Sonenshein
G E
GE
D000818:Animals; D001011:Aorta; D001483:Base Sequence; D001665:Binding Sites; D002417:Cattle; D002453:Cell Cycle; D018797:Cell Cycle Proteins; D002478:Cells, Cultured; D003094:Collagen / Q000096:biosynthesis* / Q000235:genetics*; D016895:Culture Media, Serum-Free; D004268:DNA-Binding Proteins / Q000096:biosynthesis* / Q000378:metabolism; D003609:Dactinomycin / Q000494:pharmacology; D004815:Epidermal Growth Factor / Q000494:pharmacology; D005260:Female; D016193:G1 Phase; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology; D007700:Kinetics; D008969:Molecular Sequence Data; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000378:metabolism*; D009838:Oligodeoxyribonucleotides; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000378:metabolism; D011994:Recombinant Proteins / Q000096:biosynthesis; D016196:S Phase; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D015534:Trans-Activators; D014157:Transcription Factors / Q000096:biosynthesis* / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects; D014162:Transfection
D018797:Cell Cycle Proteins; D016895:Culture Media, Serum-Free; D004268:DNA-Binding Proteins; C064352:MYBL2 protein, human; D009838:Oligodeoxyribonucleotides; D012333:RNA, Messenger; D011994:Recombinant Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D003609:Dactinomycin; D004815:Epidermal Growth Factor; D007334:Insulin-Like Growth Factor I; D003094:Collagen; D013755:Tetradecanoylphorbol Acetate