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Muscle‐Specific RING Finger 1 (MuRF1) Dependent Activation of Dual‐specificity Phosphatase 4 (Dusp4) Under Neurogenic Atrophy Conditions
Author(s) -
Haddock Ashley,
Waddell David
Publication year - 2015
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.29.1_supplement.lb709
Subject(s) - myod , psychological repression , reporter gene , myogenin , microbiology and biotechnology , muscle atrophy , transfection , mutant , gene expression , gene , biology , chemistry , biochemistry , genetics , atrophy
Skeletal muscle atrophy is the result of many physiological conditions, including denervation, corticosteroid treatment, and aging. The E3 ubiquitin ligase, MuRF1, is induced under atrophic conditions and is believed to play a role in protein degradation in wasting muscle. However, the data described in this study provides evidence that MuRF1 may also act as a transcriptional modulator of atrophy‐induced gene activity, including the regulation of Dusp4 expression. In order to characterize the transcriptional regulation of Dusp4, reporter gene constructs with fragments of the proximal promoter region of the gene were developed, transfected into C 2 C 12 cells with or without a MuRF1 expression plasmid and analyzed for differences in reporter gene activity. The Dusp4 reporters showed repressed activity in cells ectopically expressing MuRF1 compared to cells that did not overexpress MuRF1. Interestingly, overexpression of the myogenic regulatory factors (MRFs), MyoD and myogenin, also caused repression of the Dusp4 reporter constructs, while co‐overexpression of MuRF1 with MyoD or Myogenin resulted in cooperative repression of reporter gene activity. Mutagenesis of the single conserved E‐box in the Dusp4 proximal promoter resulted in a 20‐fold repression in reporter gene activity, but the trend in cooperative repression was still observed. To further characterize the role of MuRF1 in the repression of Dusp4, a MuRF1 RING domain mutant was created. The MuRF1 RING mutant failed to cooperate with the MRFs to repress the Dusp4 reporter gene activity, suggesting that catalytic activity is required for transcriptional regulation by MuRF1. This data offers evidence that MuRF1 may act as a transcriptional modulator of atrophy‐induced gene expression.