Quantitative proteomic identification of MAZ as a transcriptional regulator of muscle-specific genes in skeletal and cardiac myocytes.
We identified a conserved sequence within the Muscle creatine kinase (MCK) promoter that is critical for high-level activity in skeletal and cardiac myocytes (MCK Promoter Element X [MPEX]). After selectively enriching for MPEX-binding factor(s) (MPEX-BFs), ICAT-based quantitative proteomics was used to identify MPEX-BF candidates, one of which was MAZ (Myc-associated zinc finger protein). MAZ transactivates the MCK promoter and binds the MPEX site in vitro, and chromatin immunoprecipitation analysis demonstrates enrichment of MAZ at the endogenous MCK promoter and other muscle gene promoters (Skeletal alpha-actin, Desmin, and alpha-Myosin heavy chain) in skeletal and cardiac myocytes. Consistent with its role in muscle gene transcription, MAZ transcripts and DNA-binding activity are upregulated during skeletal myocyte differentiation. Furthermore, MAZ was shown to bind numerous sequences (e.g., CTCCTCCC and CTCCACCC) that diverge from the GA box binding motif. Alternate motifs were identified in many muscle promoters, including Myogenin and MEF2C, and one motif was shown to be critical for Six4 promoter activity in both skeletal and cardiac myocytes. Interestingly, MAZ occupies and is able to transactivate the Six4 promoter in skeletal but not cardiac myocytes. Taken together, these findings are consistent with a previously unrecognized role for MAZ in muscle gene regulation.
Himeda
Charis L
CL
Department of Biochemistry, University of Washington, Seattle, WA 98195, USA.
Ranish
Jeffrey A
JA
Hauschka
Stephen D
SD
D020816:Amino Acid Motifs; D000818:Animals; D001483:Base Sequence; D002454:Cell Differentiation; D002457:Cell Extracts; D002467:Cell Nucleus / Q000378:metabolism; D002478:Cells, Cultured; D052283:Creatine Kinase, MM Form / Q000235:genetics; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D018398:Homeodomain Proteins / Q000235:genetics; D051379:Mice; D008969:Molecular Sequence Data; D009124:Muscle Proteins / Q000235:genetics*; D018482:Muscle, Skeletal / Q000166:cytology*; D032383:Myocytes, Cardiac / Q000378:metabolism*; D009928:Organ Specificity / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D040901:Proteomics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D015534:Trans-Activators / Q000235:genetics; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D015854:Up-Regulation / Q000235:genetics
D002457:Cell Extracts; D004268:DNA-Binding Proteins; D018398:Homeodomain Proteins; D009124:Muscle Proteins; D012333:RNA, Messenger; C098490:Six4 protein, mouse; D015534:Trans-Activators; D014157:Transcription Factors; C076035:c-MYC-associated zinc finger protein; D052283:Creatine Kinase, MM Form