Zfp36l1 safeguards genome stability during myogenesis by regulating p21-E2F1-Rad51 DNA repair signaling

Skeletal muscle differentiation, a crucial process for muscle development and repair, paradoxically relies on transient DNA strand breaks (DSBs). However, an excess of DNA damage can severely impede myogenic progression, leading to impaired muscle function and regeneration. The RNA-binding protein Zfp36l1 is known to be expressed in skeletal muscle and contributes to its regeneration, yet its specific role in maintaining genome stability during this delicate balance of DNA damage in myogenesis remained undefined. Understanding this mechanism could offer new insights into sarcopenia and other muscle diseases linked to genomic instability.

Researchers investigated Zfp36l1's role in DNA damage regulation during myogenesis using C2C12 myoblast cells. They employed both loss-of-function (silencing Zfp36l1) and gain-of-function (overexpressing Zfp36l1) assays. Key experiments included RNA-seq for transcriptomic profiling, gene set enrichment analysis, and rescue experiments involving co-silencing p21. Primary endpoints assessed were DSB accumulation, G0/G1 cell cycle arrest, apoptosis, and the expression of DNA repair factors like Rad51 and Brca1 to elucidate the underlying molecular mechanisms.

Zfp36l1 expression was strongly induced during early myogenic differentiation, coinciding with the physiological onset of DSBs. Functional assays revealed that silencing Zfp36l1 aggravated DSB accumulation, reinforced G0/G1 cell cycle arrest, and promoted apoptosis. Conversely, Zfp36l1 overexpression attenuated these abnormalities. Transcriptomic profiling via RNA-seq showed that Zfp36l1 knockdown impaired homologous recombination (HR)-mediated DNA repair by downregulating core repair factors, including Rad51 and Brca1. Gene set enrichment analysis further confirmed significant suppression of the HR-dependent DSB repair pathway. Mechanistically, Zfp36l1 regulates HR repair by suppressing p21 expression, thereby relieving inhibition of E2F1-mediated Rad51 transcription. >Co-silencing p21 restored Rad51 expression and significantly reduced DNA damage in Zfp36l1-knockdown cells, confirming the critical role of the p21-E2F1-Rad51 axis.