Abstract Body: Objective: HnRNPA1 is an important member of the HNRNP family, serves multiple functions. The long noncoding RNA Ppp1r1b is a key regulator of myogenesis in cardiac and skeletal muscle development. This study aimed to investigate the role of hnRNPA1 in Ppp1r1b-lncRNA mediated myogenesis and identify the underlying molecular mechanisms.
Methods: Ppp1r1b-lncRNA: protein complex was isolated by RNA pulldown assay. The corresponding proteins were identified by mass spectrometry. The binding sites of hnRNPA1 and EZH2 on Ppp1r1b-lncRNA were further evaluated by RNA pulldown assay and western blotting. After downregulation of hnRNPA1, expression of muscle development related genes was measured by qRT-PCR and western blot analysis. Furthermore, EZH2 RIP (RNA Immunoprecipitation), H3K27me3 CHIP (Chromatin Immunoprecipitation) and Ppp1r1b-lncRNA CHIRP (Chromatin Isolation by RNA Purification) were applied.
Results: HnRNPA1 and EZH2 both bind to Ppp1r1b-lncRNA and their bindng sites are located at different positions. EZH2 RIP assay and H3K27me3 CHIP show decreased Ppp1r1b-lncRNA/EZH2 interaction and corresponded decreased H3K27me3 modification after downregulation of hnRNPA1. The expression of myogenic diffrentiation related genes was significantly suppressed by hnRNPA1-RNAi while CHIRP assay indicated elevated interaction of Ppp1r1b-lncRNA with Myod1 and Myogenin promoter.
Conclusions: HnRNPA1 facilitates the integrity of Ppp1r1b-lncRNA/PRC2 complex, which preserves correct regulation of myogenesis gene expression. After hnRNPA1 suppression, the elevated promoter occupancy of Ppp1r1b-lncRNA corresponds with transcriptional repression. The hnRNPA1/Ppp1r1b lncRNA/PRC2 complex regulatory axis is a potential therapeutic target during heart and skeletal muscle development.