PRMT1-mediated Methylation Of The Spliceosome-associated Proteins Regulates RNA Splicing

Methylation,including arginine methylation and lysine methylation,is one type of posttranslational modifications(PTMs)in eukaryotes.Arginine methylation,catalyzed by Protein Arginine Methyltransferases(PRMTs),is an important way of epigenetic regulation,which is widely existing in eukaryotes.Protein Arginine Methyltransferase(PRMT1)is a type I PRMTs and catalyzes the formation of mono-methylation and asymmetric di-methylation of arginine residue.PRMT1 participates in many physilogical and pathological processes and the methylation mediated by PRMT1 is indispensable in these processes.RNA splicing plays an essential role in the regulation of eukaryotic gene expression and maintaining the normal growth and development of cells.The regulation of RNA splicing requires the cooperation of many RNA-binding proteins.These proteins often undergo arginine methylation,and the methylated region is often the protein-RNA binding region.RNA splicing is precisely regulated by a protein-RNA complex called spliceosome.If such regulation is disrupted,abnormal alternative splicing has been shown to be closely related to the occurrence and development of human diseases including cancer.However,it is still unclear whether PRMT1 regulates RNA splicing,and if so,what are the underlying molecular mechanisms.Furthermore,whether PRMT regulation of RNA splicing is linked to its role in disease development,such as cancer,remains elusive.Aiming to investigate whether PRMT1 has the ability to regulate RNA splicing,we used high-throughput sequencing techniques including RASL-seq and RNA-seq to comprehensively analyze the effect of PRMT 1 on alternative splicing events.PRMT1 was found to have a wide-spreading role in RNA alternative splicing.We then used mass spectrometry and SILAC combined with high-resolution mass spectrometry separately to identify the interacting protein networks and substrate of PRMT 1.It was found that a large group of proteins in the spliceosome not only interacted with PRMT1,but also were PRMT1 substrates.To underscore the clinical significance of PRMT1-regulated alternative splicing events,some of them were found to have different splicing patterns between normal and tumor tissues.One of the PRMT1-substrates RBMX,a protein in the spliceosome,could coregulate these genes with PRMT1.In summary,the current study described a potential mechanism by which PRMT1 is involved in carcinogenesis,such that PRMT1 interacts with and methylates components in the spliceosome,which could potentially affect the activities of splicesome,and therefor gene alternative splicing.Combinational therapy of small molecule inhibitor targeting PRMT1 and the splicesome will provide a new avenue for treating PRMT1-related cancers.