title: Structure and function of the upstream promotor of the human Mafbx gene: the proximal upstream promotor modulates tissue-specificity.
abstract: Muscle loss has been linked to increased expression of an ubiquitin ligase termed muscle atrophy F-box (MAFbx), a nuclear protein involved in degradation of MyoD. To gain insights into mechanisms by which the human MAFbx gene is controlled, the structure of its upstream promotor were studied, and its expression in cultured cells was characterized. Expression of MAFbx was found only in cells of muscle lineage. A reporter gene controlled by 948 bases of human MAFbx upstream promotor displayed similar cell-type selectivity. MAFbx levels were greatly enhanced upon myogenic differentiation of C2C12 myoblasts, and differentiation markedly increased activity of a reporter gene constructed with 400 bp of upstream promotor from the MAFbx gene. The core promotor spanned approximately 160 bases beginning at -241 bp upstream of the first codon, included potential binding sites for MyoD and myogenin, and was highly conserved among mouse, rat, and humanMAFbx genes. The major transcription start site for the human MAFbx gene was 340 bases upstream of the ATG and was localized the highly conserved region of 140 bp. The findings indicate an important role for the immediate upstream promotor of the human MAFbx gene in mediating its developmental expression and tissue specificity.
authors.affiliation: VA Rehabilitation Research and Development Service Center of Excellence, Bronx VA Medical Center, Bronx, New York, USA.
authors.forename: Weidong
authors.initials: W
authors.lastname: Zhao
authors.forename: Yong
authors.initials: Y
authors.lastname: Wu
authors.forename: Jingbo
authors.initials: J
authors.lastname: Zhao
authors.forename: Shuang
authors.initials: S
authors.lastname: Guo
authors.forename: William A
authors.initials: WA
authors.lastname: Bauman
authors.forename: Christopher P
authors.initials: CP
authors.lastname: Cardozo
mesh_terms: D000818:Animals; D001483:Base Sequence; D016466:CHO Cells; D019556:COS Cells; D002454:Cell Differentiation; D002522:Chlorocebus aethiops; D006224:Cricetinae; D003412:Cricetulus; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D009124:Muscle Proteins / Q000235:genetics* / Q000378:metabolism; D009132:Muscles / Q000378:metabolism; D009928:Organ Specificity / Q000235:genetics*; D016716:PC12 Cells; D011401:Promoter Regions, Genetic; D051381:Rats; D044843:SKP Cullin F-Box Protein Ligases / Q000235:genetics* / Q000378:metabolism; D016415:Sequence Alignment; D014162:Transfection
chemical_list: D009124:Muscle Proteins; C440907:FBXO32 protein, human; D044843:SKP Cullin F-Box Protein Ligases