Isolation and characterization of chicken TaxREB107, a putative DNA binding protein abundantly expressed in muscle.
Myogenic regulatory factors (MRFs) are vital transcription factors that act at multiple points during development to establish the skeletal muscle phenotype. This class of muscle-restricted, basic helix-loop-helix (bHLH) proteins acts in concert with additional transcriptional modulators to precisely control muscle gene expression. We have isolated the chicken homologue of Tax responsive element binding protein 107 (TaxREB107). The cDNA is 83% homologous at the amino acid level to human and mouse TaxREB107 and contains a centrally located leucine zipper motif. Northern analysis demonstrated that the gene is expressed in multiple tissues including skeletal muscle. Immunofluorescent staining revealed that the cTaxREB107 protein is located in both the nuclear and cytoplasmic compartments. Distinct localization to the nucleoli supports the evidence that TaxREB107 is a ribosomal protein. Because TaxREB proteins also are implicated in transcriptional regulation, we overexpressed cTaxREB107 in embryonic myoblasts. cTaxREB107 increased troponin I reporter gene activity as well as MRF-directed transcription from a multimerized skeletal muscle E-box reporter gene (4Rtk-luc). However, cotransfection of expression plasmids coding for MyoD and cTaxREB107 did not produce an increase in 4Rtk-luc suggesting that cTaxREB107 enhances myogenic gene transcription through a means independent of a physical association with MyoD. In conclusion, our results define a role for cTaxREB107 during avian myogenesis as a positive modulator of skeletal muscle gene expression.
Thomson
S R
SR
Department of Poultry Science, The Pennsylvania State University, 206 Henning, University Park, PA 16802, USA.
Johnson
S E
SE
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D002467:Cell Nucleus / Q000378:metabolism; D002645:Chickens / Q000235:genetics*; D003593:Cytoplasm / Q000378:metabolism; D018076:DNA, Complementary / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification; D004268:DNA-Binding Proteins / Q000235:genetics*; D015870:Gene Expression; D018507:Gene Expression Regulation, Developmental; D006801:Humans; D008156:Luciferases / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D009132:Muscles / Q000166:cytology / Q000196:embryology / Q000378:metabolism*; D017570:MyoD Protein / Q000235:genetics / Q000502:physiology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D014018:Tissue Distribution; D014158:Transcription, Genetic
D018076:DNA, Complementary; D004268:DNA-Binding Proteins; D017570:MyoD Protein; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; C093544:tax-responsive-element-binding protein 107, mouse; D008156:Luciferases