CLP-1 associates with MyoD and HDAC to restore skeletal muscle cell regeneration

Department of Cell Biology, Center for Cardiovascular and Muscle Research, State University of New York Downstate Medical Center, Brooklyn, New York, NY 11203, USA.
Journal of Cell Science (Impact Factor: 5.43). 10/2010; 123(Pt 21):3789-95. DOI: 10.1242/jcs.073387
Source: PubMed


Emerging evidence suggests that eukaryotic gene transcription is regulated primarily at the elongation stage by association and dissociation of the inhibitory protein cardiac lineage protein 1 (CLP-1/HEXIM1) from the positive transcription elongation factor b (P-TEFb) complex. It was reported recently that P-TEFb interacts with skeletal muscle-specific regulatory factor, MyoD, suggesting a linkage between CLP-1-mediated control of transcription and skeletal myogenesis. To examine this, we produced CLP-1 knockdown skeletal muscle C2C12 cells by homologous recombination, and demonstrated that the C2C12 CLP-1 +/- cells failed to differentiate when challenged by low serum in the medium. We also showed that CLP-1 interacts with both MyoD and histone deacetylases (HDACs) maximally at the early stage of differentiation of C2C12 cells. This led us to hypothesize that the association might be crucial to inhibition of MyoD-target proliferative genes. Chromatin immunoprecipitation analysis revealed that the CLP-1/MyoD/HDAC complex binds to the promoter of the cyclin D1 gene, which is downregulated in differentiated muscle cells. These findings suggest a novel transcriptional paradigm whereby CLP-1, in conjunction with MyoD and HDAC, acts to inhibit growth-related gene expression, a requirement for myoblasts to exit the cell cycle and transit to myotubes.

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    • "Rabbit monoclonal anti-Cyclin-D1 was used to label cells in G1-S transition as has been shown previously in retinae (Albarracin and Valter, 2012; Bienvenu et al., 2010). The anti-Cyclin-D1 antibody produces an expected band of about 33 kDa on immunoblots from mouse testes (see manufacturer's data sheet and McIver et al., 2012) and regenerating mouse skeletal muscle (Galatioto et al., 2010). Rabbit monoclonal anti-1098 bp Ki-67 motif-containing cDNA fragment (Ki-67) was used to label all cycling cells, those in G1, S, G2 and M, as has been shown previously in retinae (Glaschke et al., 2011) and in the mouse small intestine (Bergner et al., 2014). "
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    • "The 7SK snRNA-bound HEXIM1 binds to P-TEFb through the interaction with cyclin T1, resulting in suppressing the kinase activity of P-TEFb [25,57]. In addition to cyclin T1, other HEXIM1 binding proteins have been reported [32–38]. We previously identified NPM, HDM2, and p53 as HEXIM1 binding proteins [34,35,39]. "
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