The Biological Function Of Protein Arginine Methyltransferase PRMT3

Post-translational modification(PTM)refers to the covalent and generally enzymatic modification of proteins following protein biosynthesis.PTM is important for the regulation of cellular processes,through influencing subcellular localization,function,and complex formation of proteins.Arginine methylation is a common type of PTM catalyzed by protein arginine methyltransferase(PRMTs),which catalyze the transfer of a methyl group from S-adenosylmethionine(SAM)to the guanidino nitrogen atoms of arginine.There are mainly three forms of methylarginines identified in eukaryotes: ω-NG-mono-methylarginine(MMA),ω-NG,NG-asymmetric methylarginine(a DMA)and ω-NG,NG-symmetric methylarginine(sDMA).Nine protein arginine methyltransferases(PRMTs)are encoded in mammalian.PRMTs fall into three categories according to their catalytic activity: type I(PRMT1,PRMT2,PRMT3,PRMT4,PRMT6 and PRMT8)and type II(PRMT5 and PRMT9)enzymes carry out the formation of MMA as an intermediate before the establishment of a DMA or s DMA,respectively.PRMT7 is a type III enzyme that catalyzes only the formation of MMA.Protein arginine methylation control many important cell biological processes including cell growth,proliferation and differentiation.The abnormality of protein arginine methylation is closely related to the occurrence of tumor,typeⅡdiabetes and other diseases.Therefore,understanding the functions and working mechanisms of PRMTs,the mediators of arginine methylation,can provide new ideas for the prevention, diagnosis and treatment of cancer.In mammalian,arginine methyltransferase 3(PRMT3)is located exclusively in cytosol and its zinc finger domain anchors it to different substrates.RPS2,the von Hippel–Lindau(VHL)tumour suppressor protein,and the DAL1 tumour suppressor protein are reported PRMT3 substrates,and their interactions with PRMT3 have been found important to regulate p53,or regulate PRMT3 activity.However,the study of PRMT3 is still limited.Its biological function and its arginine methylation substrates needs to be further explored.In this study,a PRMT3-knockout non-small cell lung cancer A549 cell line was established by using CRISPR/Cas9.Depletion of PRMT3 significantly enhanced the clone formation capability of A549 cells,greatly changed cell cycle,but had no effect on cell migration.Certain possible substrates of PRMT3 had been identified through antibody enrichment and mass spectrometry,which lays a foundation for further exploring the biological function of PRMT3 and its significance in the diagnosis and treatment of lung cancer.In addition to exploring the function of arginine methyltransferase,it is also important to study the methylation modification of critical proteins closely related to tumor occurrence,and to understand the function of the methylation in tumor occurrence.For example,PRMTs can direct methylate histone and regulate transcription.PRMT1 and PRMT5 can methylate epidermal growth factor receptor respectively,leading to different consequence in signal transduction and cancer cell proliferation.Hippo-YAP pathway is an important signal transduction pathway,which can affect cell proliferation and apoptosis,regulate organ size and affect the development of tumor.YAP protein is the core protein in this pathway,and its abnormal expression or activation is closely related to the occurrence of tumor.However,it is not clear whether YAP protein could be methylated at its arginine residues.In this study,we identified 3 arginine methylation sites in YAP protein using proteomic analysis.It was found that the methylaton of Arg124 and Arg378 sites affected the phosphorylation of Ser127,and the methylation of Arg327 affected the expression of Hippo-YAP target genes.These results can help us further understand regulatory mechanism of YAP,which provides a new theoretical basis for targeting YAP in the treatment of cancer.