Protein arginine methyltransferase 5 (PRMT5) has been implicated as an important regulator of many cellular processes and signaling pathways,including chromatin remodeling,RNA splicing,DNA transcription,and cell proliferation.Therefore,structural and functional studies on PRMT5 are quite important.The full length ofPRMT5 gene was cloned into vector pGEX-4T-1,resulting in only low expression levels in Escherichia coli (E.colO.Here,it was showed that the several N-terminal amino acids deletions could result in a significant increase in the amount of soluble ft"action,while one of them did not affect the protein-arginine methyltransferase activity.And it was also found that the N-terminal 15 amino acids region of PRMT5 may be important for the catalytic activity.

Objective:To investigate the arginine (Arg) sites in splicing factor 2/alternative splicing factor (SF2/ASF) methylated by protein arginine methyltransferase 1 (PRMT1). Methods:Wild-type and Arg93,Arg97,Arg109 mutant SF2/ASF plasmids were constructed,and GST-PRMT1,GST-SF2/ASF and arginine mutant GST-SF2/ASF fusion proteins were induced and purified. Methylation activity of PRMT1 on wild-type or mutant SF2/ASF protein and methylated sites of SF2/ASF were examined by methylation assay. The effect of SF2/ASF methylation on its subcellular localization was analyzed by immunofluorescence assay.Results:PRMT1 induced methylation of SF2/ASF at arginine,and PRMT1 did not methylate SF2/ASF when SF2/ASF was mutant at Arg93,Arg97 or Arg109,with Arg97 mutation showing the most profound inhibitory effect. Methylation of SF2/ASF did not affect its subcellular localization.Conclusion:SF2/ASF is a newly identified substrate of PRMT1; Arg93,Arg97 and Arg 109 are the three methylation sites in SF2/ASF,and Arg97 is the main methylation site. Methylation of SF2/ASF does not affect its subcellular localization.