VIRMA-mediated SHQ1 m6A modification enhances liver regeneration through an HNRNPA2B1-dependent mechanism

Abstract

N6-Methyladenosine (m6A) modification is a crucial post-transcriptional regulatory mechanism and the most abundant and highly conserved RNA epigenetic modification in eukaryotes. Previous studies have indicated the involvement of m6A modification in various tissue regeneration processes, including liver regeneration. Vir-like m6A methyltransferase associated protein (VIRMA) is an m6A methyltransferase with robust methylation capability. However, its role in liver regeneration remains poorly understood. In this study, we generated liver-specific Virma knockout mice using the Cre-loxP system and investigated the biological functions of VIRMA in liver regeneration using both the Associating Liver Partition and Portal vein Ligation for Staged Hepatectomy (ALPPS) mouse model and the carbon tetrachloride (CCl₄) mouse model. The expression level of VIRMA was rapidly up-regulated after ALPPS surgery and gradually down-regulated during liver repair. Virma deficiency significantly impaired liver regeneration capacity and disrupted cell cycle progression. Methylated RNA immunoprecipitation sequencing (MeRIP-seq) analysis revealed that Shq1 is an effective downstream target of VIRMA-mediated m6A modification. The upregulation of Shq1 enhanced the proliferation ability of cells, which was attenuated by the specific AKT inhibitor ipatasertib. Supplementation of Shq1 in vivo alleviated the liver cell proliferation inhibition caused by Virma deficiency. Furthermore, the m6A-binding protein heterogeneous nuclear ribonucleoprotein a2b1 (HNRNPA2B1) enhanced the mRNA stability of Shq1. Mechanistically, Virma deficiency resulted in decreased m6A modification on Shq1 mRNA, leading to reduced binding ability of m6A-binding protein HNRNPA2B1 with Shq1, thereby decreasing the mRNA stability of Shq1 and reducing its protein expression level. Downregulation of Shq1 inhibited the PI3K/AKT pathway, thereby suppressing cell proliferation and cell cycle progression, ultimately impeding liver regeneration. In summary, our results demonstrate that VIRMA plays a critical role in promoting liver regeneration by regulating m6A modification, providing valuable insights into the epigenetic regulation during liver regeneration.