Heterogeneous nuclear ribonucleoprotein A1 (hnRNPA1) is a multifunctional RNA-binding protein of the hnRNP family, yet its role in long non-coding RNA (lncRNA)-mediated epigenetic regulation during myogenesis remains unclear. The lncRNA Ppp1r1b-lncRNA is an established regulator of myogenesis that functions through interaction with Polycomb repressive complex 2 (PRC2) at myogenic gene promoters. Here, we investigated the role of hnRNPA1 in Ppp1r1b-lncRNA-mediated regulation of myogenesis. Fluorescence in situ hybridization (FISH) revealed the subcellular localization of Ppp1r1b-lncRNA, and RNA pulldown coupled with mass spectrometry identified associated proteins. Both hnRNPA1 and EZH2 were found to bind Ppp1r1b-lncRNA, but at distinct regions. Knockdown of hnRNPA1 in mouse C2C12 myoblasts reduced the interaction between Ppp1r1b-lncRNA and EZH2, as determined by RNA immunoprecipitation (RIP), decreased promoter occupancy of Ppp1r1b-lncRNA, as assessed by chromatin isolation by RNA purification (CHIRP), and reduced H3K27me3 levels at the MyoD1 and Myogenin promoters, as shown by chromatin immunoprecipitation (ChIP). These changes led to increased expression of muscle-specific transcription factors and sarcomeric genes, thereby disrupting the undifferentiated state. Furthermore, hnRNPA1 knockdown disrupted the interaction between the human ortholog PPP1R1B-lncRNA and PRC2 in human skeletal muscle precursor cells (hSMPCs). Together, these findings demonstrate that hnRNPA1 maintains the integrity of the Ppp1r1b-lncRNA-PRC2 complex and ensures proper epigenetic regulation of myogenic gene expression. This conserved hnRNPA1-Ppp1r1b-lncRNA-PRC2 regulatory axis represents a potential therapeutic target for muscle regeneration.
Kang et al. (2026) studied this question.