Regulation of alpha-tropomyosin and N5 genes by a shared enhancer. Modular structure and hierarchical organization.
We have identified a 99-base pair (bp) tandem repeat consisting of two modules/repeat: a 40-bp-long d(CA.GT)20 potential Z-DNA sequence and a 59-bp-long unique sequence. This repeat is located between and differentially regulates two transcription units, rat alpha-tropomyosin and N5, organized in "head-to-head" orientation. Transient expression experiments showed orientation- and position-independent enhancer activity of the 99-bp repeat in a tissue-specific and developmental manner. Deletion analysis revealed a hierarchical organization establishing the two modules as protoenhancers. Southwestern blot analysis of crude nuclear extracts identified at least six C2C12 myotube nuclear proteins binding to the 99-bp repeat. These observations demonstrate a mammalian gene regulatory sequence structurally and functionally organized like the simian virus 40 viral enhancer and confirm in a specific gene context the contribution of a d(CA.GT)20 tract in transcriptional regulatory mechanisms as a protoenhancer.
Herrera
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VL
Section of Molecular Genetics, Whitaker Cardiovascular Institute, Boston University School of Medicine, Massachusetts 02118.
Ruiz-Opazo
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D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D015500:Chloramphenicol O-Acetyltransferase / Q000235:genetics; D004247:DNA / Q000235:genetics; D004274:DNA, Recombinant; D004742:Enhancer Elements, Genetic; D005091:Exons; D005786:Gene Expression Regulation; D005814:Genes, Viral; D051379:Mice; D008969:Molecular Sequence Data; D009124:Muscle Proteins / Q000235:genetics*; D009132:Muscles / Q000032:analysis / Q000378:metabolism; D009690:Nucleic Acid Conformation; D009693:Nucleic Acid Hybridization; D012333:RNA, Messenger / Q000032:analysis / Q000235:genetics; D051381:Rats; D011919:Rats, Inbred Strains; D012045:Regulatory Sequences, Nucleic Acid; D012091:Repetitive Sequences, Nucleic Acid; D013539:Simian virus 40 / Q000235:genetics; D014158:Transcription, Genetic; D014162:Transfection; D014335:Tropomyosin / Q000235:genetics*
D004274:DNA, Recombinant; D009124:Muscle Proteins; D012333:RNA, Messenger; D014335:Tropomyosin; D004247:DNA; D015500:Chloramphenicol O-Acetyltransferase