Abstract
The myogenic factor MyoD regulates skeletal muscle differentiation by interacting with a variety of chromatin-modifying complexes. Although MyoD can induce and maintain chromatin accessibility at its target genes, its binding and trans-activation ability can be limited by some types of not fully characterized epigenetic constraints. In this work we analysed the role of PARP1 in regulating MyoD-dependent gene expression. PARP1 is a chromatin-associated enzyme, playing a well recognized role in DNA repair and that is implicated in transcriptional regulation. PARP1 affects gene expression through multiple mechanisms, often involving the Poly(ADP-ribosyl)ation of chromatin proteins. In line with PARP1 down-regulation during differentiation, we observed that PARP1 depletion boosts the up-regulation of MyoD targets, such as p57, myogenin, Mef2C and p21, while its re-expression reverts this effect. We also found that PARP1 interacts with some MyoD-binding regions and that its presence, independently of the enzymatic activity, interferes with MyoD recruitment and gene induction. We finally suggest a relationship between the binding of PARP1 and the loss of the activating histone modification H3K4me3 at MyoD-binding regions. This work highlights not only a novel player in the epigenetic control of myogenesis, but also a repressive and catalytic-independent mechanisms by which PARP1 regulates transcription.
Highlights
Skeletal muscle differentiation is determined by the activation of a complex program of gene expression, which involves the temporally regulated induction of muscle-specific genes as well as of cell cycle inhibitors that ensure cell cycle exit of differentiating c ells[1]
We first examined the effects of PARP1 depletion on muscle gene expression in C2.7 cells stably knocked-down for PARP1
Cell pools stably transduced with the short hairpin RNA for PARP1 (shPARP1) or the empty control vector were isolated by puromycin selection and tested for the knockdown efficiency
Summary
Skeletal muscle differentiation is determined by the activation of a complex program of gene expression, which involves the temporally regulated induction of muscle-specific genes as well as of cell cycle inhibitors that ensure cell cycle exit of differentiating c ells[1]. The best established mechanisms by which the myogenic factor creates a chromatin environment permissive for transcription involves the recruitment of the histone acetylases p300/CBP and pCAF6–8 and the chromatin remodelling complex SWI/SNF9,10 on the targeted regulatory-regions. MyoD can initiate chromatin remodeling and histone modifications at target sites in heterochromatin, its binding and transactivation capability are limited by some types of epigenetic constraints. We have recently shown that accumulation of H3 lysine 9 dimethylation (H3K9me2) at a critical regulatory region of the MyoD target p57kip[2], hinders the binding of MyoD and the consequent reorganization of the chromatin architecture, preventing the up-regulation of the gene in muscle cell types un-responsive for p57 induction[17]. Inactive PARP1 positively regulates a pluripotency gene expression program in embryonic stem c ells[52]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
