title: Telokin expression in A10 smooth muscle cells requires serum response factor.
abstract: Telokin transcription is initiated from a smooth muscle-specific promoter located in an intron of the smooth muscle myosin light chain kinase gene. We have previously identified a 310-base pair fragment of the promoter that mediates A10 smooth muscle cell-specific expression of telokin. In the current study, telokin-luciferase reporter gene assays in A10 cells and REF52 nonmuscle cells revealed that the promoter region between -81 and +80 contains the regulatory elements required to mediate the in vitro cell specificity of the promoter. Several positive-acting elements, including an E box, myocyte enhancer factor 2 (MEF2)-TATA box, and CArG-serum response element, were identified within this region. Telokin transcription in A10 smooth muscle cells requires all three transcription initiation sites and an AT-rich sequence between -71 and -62 that includes a TATA box. MEF2 interacts with the AT-rich region with low affinity; however, MEF2 binding is not required for transcriptional activity in A10 cells. Binding of serum response factor (SRF) to a CArG element proximal to the TATA sequence is also critical for high levels of transcription in A10 cells. Together these data suggest that an AT-rich motif, acting in concert with SRF and an unusual transcription initiation mechanism, is required for the cell-specific expression of the telokin promoter in A10 smooth muscle cells.
authors.affiliation: Department of Physiology and Biophysics, Indiana University School of Medicine, Indianapolis 46202, USA.
authors.forename: B P
authors.initials: BP
authors.lastname: Herring
authors.forename: A F
authors.initials: AF
authors.lastname: Smith
mesh_terms: D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000378:metabolism / Q000502:physiology*; D005786:Gene Expression Regulation; D064326:MEF2 Transcription Factors; D008969:Molecular Sequence Data; D009124:Muscle Proteins / Q000235:genetics*; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000502:physiology*; D018006:Myogenic Regulatory Factors; D009219:Myosin-Light-Chain Kinase; D009687:Nuclear Proteins / Q000502:physiology*; D010446:Peptide Fragments; D010455:Peptides; D011401:Promoter Regions, Genetic; D051381:Rats; D026362:Serum Response Factor; D014157:Transcription Factors / Q000378:metabolism; D015533:Transcriptional Activation
chemical_list: D004268:DNA-Binding Proteins; D064326:MEF2 Transcription Factors; D009124:Muscle Proteins; D018006:Myogenic Regulatory Factors; D009687:Nuclear Proteins; D010446:Peptide Fragments; D010455:Peptides; D026362:Serum Response Factor; D014157:Transcription Factors; C060640:telokin; D009219:Myosin-Light-Chain Kinase