N6-methyladenosine (m6A) is a chemical modification of adenosine in RNA that plays a crucial role in the regulation of gene expression. As the most abundant form of RNA chemical methylation, m6A is aberrantly expressed in hepatocellular carcinoma (HCC), where it affects multiple biological processes including targeted RNA splicing, transport, degradation, stabilization, and translation. RBM15B (RNA-binding motif protein 15B), is a gene that encodes a protein involved in RNA processing and regulation. RBM15B is a member of the RNA-binding motif (RBM) protein family, which plays diverse roles in post-transcriptional gene regulation. RBM15B is proven to be involved in mRNA processing, including pre-mRNA splicing, mRNA transport, and mRNA stability. It may also participate in other RNA-related processes such as mRNA translation and RNA decay. We investigated the phenotypes of RBM15B in HCC using the TCGA database, in-vitro, and in vivo assays. m6A dot blot was used to assess RNA methylation levels and Merip-seq/RNA-seq were employed to explore the biological effects and potential mechanisms of RBM15B in HCC. We hypothesized that RBM15B may regulate ITSN2 expression in HCC. To test this, RNA immunoprecipitation (RIP) followed by qRT-PCR was applied for the identification and characterization of target ITSN2 mRNA that interacted with RNA binding protein IGF2BP1, which may mediate the effects of RBM15B. To further elucidate the functional relationship between RBM15B and ITSN2, we performed rescue assays of cell proliferation and migration to determine whether RBM15B over-expression is able to restore the loss of function induced by ITSN2 knockdown to an extent. High levels of RBM15B were verified by both TCGA data and our cohort. High levels of RBM15B predicted a poor prognosis. RBM15B promotes HCC propagation and invasion in vitro and in vivo. RBM15B regulates the m6A of intersectin2 (ITSN2) mRNA via insulin-like growth factor 2 mRNA binding protein 1 (IGF2BP1)-facilitated stabilization of ITSN2 mRNA. ITSN2 depletion rescued the tumor-promoting phenotype induced by RBM15B overexpression. In summary, RBM15B-regulated m6A in ITSN2 mRNA facilitates HCC progression via IGF2BP1-guided stabilization of ITSN2 mRNA. Our study illustrates the importance of the RBM15B-IGF2BP1-ITSN2 regulatory axis based on m6A activity and provides new insights into epi-transcriptomic maladjustments of initiation and metastasis in HCC.
Xu et al. (Sat,) studied this question.