A 29-nucleotide DNA segment containing an evolutionarily conserved motif is required in cis for cell-type-restricted repression of the chicken alpha-smooth muscle actin gene core promoter.
A series of 5' deletion mutations of the upstream flanking sequences of the chicken alpha-smooth muscle (aortic) actin gene was prepared and inserted into the chloramphenicol acetyltransferase expression vector pSV0CAT. Deletion recombinants were transfected into fibroblasts, which actively express the alpha-smooth muscle actin gene, and primary myoblast cultures, which accumulate much lower quantities of alpha-smooth muscle actin mRNAs. The first 122 nucleotides of 5'-flanking DNA were found to contain a "core" promoter capable of accurately directing high levels of transcription in both fibroblasts and myotubes. The activity of this core promoter is modulated in fibroblasts by a "governor" element(s) located at least in part between nucleotides -257 and -123. This region contains sequences potentially conserved between mammalian and avian alpha-smooth muscle actin genes as well as one of a pair of 16-base-pair inverted CCAAT box-associated repeats which are conserved among all chordate muscle actin genes examined to date. A smaller DNA segment (-151 to -123) containing these upstream CCAAT box-associated repeats was sufficient to suppress expression of the core promoter in muscle cultures, suggesting that the upstream CCAAT box-associated repeats play a negative role in the alpha-smooth muscle actin gene promoter.
Carroll
S L
SL
Department of Cell Biology, Baylor College of Medicine, Houston, Texas 77030.
Bergsma
D J
DJ
Schwartz
R J
RJ
D000199:Actins / Q000235:genetics*; D000818:Animals; D005075:Biological Evolution; D002478:Cells, Cultured; D002645:Chickens; D004252:DNA Mutational Analysis; D005347:Fibroblasts / Q000502:physiology; D005786:Gene Expression Regulation; D009131:Muscle, Smooth, Vascular / Q000502:physiology*; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000235:genetics; D012045:Regulatory Sequences, Nucleic Acid; D012689:Sequence Homology, Nucleic Acid; D014158:Transcription, Genetic
D000199:Actins; D012333:RNA, Messenger