Zfp36l1 Inhibits DNA Damage by Regulating p21-E2F1-Rad51 Signaling During Myogenic Differentiation.

Skeletal muscle differentiation relies on transient DNA strand breaks (DSBs), yet excessive DNA damage remains harmful to myogenic progression. The RNA-binding protein Zfp36l1 is expressed in skeletal muscle and contributes to muscle regeneration; nevertheless, its role in preserving genome stability during myogenic differentiation has not been defined. Here, we investigated the role and mechanism of Zfp36l1 in regulating DNA damage using C2C12 myoblast cells, combining loss- and gain-of-function assays, RNA-seq, and rescue experiments. The results revealed that Zfp36l1 expression is strongly induced during early myogenic differentiation, coinciding with the onset of physiological DSBs. Functional assays revealed that silencing Zfp36l1 aggravates DSB accumulation, reinforces G0/G1 cell cycle arrest, and promotes apoptosis, whereas Zfp36l1 overexpression attenuates these abnormalities. Transcriptomic profiling shows that Zfp36l1 knockdown impairs homologous recombination (HR)-mediated DNA repair by downregulating core repair factors, including Rad51 and Brca1. Gene set enrichment analysis further confirms 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 restores Rad51 expression and reduces DNA damage in Zfp36l1-knockdown cells. Collectively, these findings identify Zfp36l1 as an essential safeguard of genome stability during myogenic differentiation by balancing DNA damage levels through the p21-E2F1-Rad51 signaling axis, and provide new insights into the regulatory basis of muscle development and genomic instability-associated muscle diseases.