Repression of transcriptional enhancer factor-1 and activator protein-1-dependent enhancer activity by vascular actin single-stranded DNA binding factor 2.
Transcriptional repression of the murine vascular smooth muscle alpha-actin gene in fibroblasts results from the interaction of two sequence-specific single-stranded DNA binding activities (VACssBF1 and VACssBF2) with opposite strands of an essential transcriptional enhancer factor-1 (TEF-1) element (Sun, S., Stoflet, E. S., Cogan, J. G., Strauch, A. R., and Getz, M. J. (1995) Mol. Cell. Biol. 15, 2429-2436). Here, we identify a sequence element located within a protein-coding exon of the gene that bears structural similarity with the TEF-1 enhancer. This includes a 30-base pair region of purine-pyrimidine asymmetry encompassing a perfect 6-base pair GGAATG TEF-1 recognition motif. Unlike the enhancer, however, the exon sequence exhibits no TEF-1 binding activity nor does the pyrimidine-rich strand bind VACssBF1. However, VACssBF2 interacts equally well with the purine-rich strand of both the enhancer and the exon sequence. To test the ability of VACssBF2 to independently repress transcription, the exon sequence was placed upstream of a deletionally activated promoter containing an intact TEF-1 binding site. The exon sequence repressed promoter activity, whereas a mutant deficient in VACssBF2 binding did not. Moreover, VACssBF2 similarly repressed activator protein-1-dependent transcription of a heterologous tissue factor promoter. These results suggest that VACssBF2 possesses an intrinsic ability to disrupt enhancer function independently of the enhancer-binding proteins involved.
Kelm
R J
RJ
Department of Biochemistry and Molecular Biology, Mayo Clinic/Foundation, Rochester, Minnesota 55905, USA.
Sun
S
S
Strauch
A R
AR
Getz
M J
MJ
D016475:3T3 Cells; D000199:Actins / Q000235:genetics*; D000818:Animals; D002460:Cell Line; D004277:DNA, Single-Stranded / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004742:Enhancer Elements, Genetic; D005091:Exons; D005786:Gene Expression Regulation; D051379:Mice; D008970:Molecular Weight; D009131:Muscle, Smooth, Vascular; D009687:Nuclear Proteins; D011401:Promoter Regions, Genetic; D012097:Repressor Proteins / Q000235:genetics* / Q000378:metabolism*; D000091262:TEA Domain Transcription Factors; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic
D000199:Actins; D004277:DNA, Single-Stranded; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D012097:Repressor Proteins; D000091262:TEA Domain Transcription Factors; C057182:TEAD1 protein, human; D014157:Transcription Factors