title: Competition between negative acting YY1 versus positive acting serum response factor and tinman homologue Nkx-2.5 regulates cardiac alpha-actin promoter activity.
abstract: Transcription of sarcomeric alpha-actin genes is developmentally regulated during skeletal and cardiac muscle development through fine-tuned control mechanisms involving multiple cooperative and antagonistic transcription factors. Among the cis-acting DNA elements recognized by these factors is the sequence CC(A/T)6GG of the serum response element (SRE), which is present in a number of growth factor-inducible and myogenic specified genes. We recently showed that the cardiogenic homeodomain factor, Nkx-2.5, served as a positive acting accessory factor for serum response factor (SRF) and together provided strong transcriptional activation of the cardiac alpha-actin promoter. In addition, Nkx-2.5 and SRF collaborated to activate the endogenous murine cardiac alpha-actin gene in 10T1/2 fibroblasts, by a mechanism that involved coassociation of SRF and Nkx-2.5 on intact SREs of the alpha-actin promoter. Here, we show that the second SRE of the avian cardiac alpha-actin promoter served as a binding site for Nkx-2.5, SRF, and zinc finger containing GLI-Kruppel-like factor, YY1. Expression of YY1 inhibited cardiac alpha-actin promoter activity, whereas coexpression of Nkx-2.5 and SRF was able to partially reverse YY1 repression. Displacement of YY1 binding by Nkx-2.5/SRF complex occurs through mutually exclusive binding across the CaSRE2. The interplay and functional antagonism between YY1 and Nkx-2.5/SRF might constitute a developmental as well as a physiologically regulated mechanism that modulates cardiac alpha-actin gene expression during cardiogenesis.
authors.affiliation: Department of Cell Biology, Baylor College of Medicine, Houston, Texas 77030, USA.
authors.forename: C Y
authors.initials: CY
authors.lastname: Chen
authors.forename: R J
authors.initials: RJ
authors.lastname: Schwartz
mesh_terms: D000199:Actins / Q000235:genetics*; D000818:Animals; D002478:Cells, Cultured; D002645:Chickens; D004268:DNA-Binding Proteins / Q000235:genetics*; D005347:Fibroblasts / Q000166:cytology; D005786:Gene Expression Regulation; D000072576:Homeobox Protein Nkx-2.5; D018398:Homeodomain Proteins / Q000235:genetics*; D006801:Humans; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D009687:Nuclear Proteins / Q000235:genetics*; D011401:Promoter Regions, Genetic; D012045:Regulatory Sequences, Nucleic Acid; D012097:Repressor Proteins / Q000235:genetics*; D026362:Serum Response Factor; D014157:Transcription Factors / Q000235:genetics*; D015533:Transcriptional Activation; D044767:Ubiquitin-Protein Ligases; D029867:Xenopus Proteins; D016335:Zinc Fingers
chemical_list: D000199:Actins; D004268:DNA-Binding Proteins; D000072576:Homeobox Protein Nkx-2.5; D018398:Homeodomain Proteins; C095552:NKX2-5 protein, human; C484469:Nkx2-5 protein, mouse; D009687:Nuclear Proteins; D012097:Repressor Proteins; D026362:Serum Response Factor; D014157:Transcription Factors; D029867:Xenopus Proteins; C084953:E4f1 protein, mouse; D044767:Ubiquitin-Protein Ligases