Identification and Characterization of Protein Arginine Methyltransferase 1 in Acanthamoeba castellanii

Protein arginine methyltransferase (PRMT) is an important epigenetic regulator in eukaryotic cells. During encystation, an essential process for Acanthamoeba survival, the expression of a lot of genes involved in the encystation process has to be regulated in order to be induced or inhibited. However, the regulation mechanism of these genes is yet unknown. In this study, the full-length 1,059 bp cDNA sequence of Acanthamoeba castellanii PRMT1 (AcPRMT1) was cloned for the first time. The AcPRMT1 protein comprised of 352 amino acids with a SAM-dependent methyltransferase PRMT-type domain. The expression level of AcPRMT1 was highly increased during encystation of A. castellanii. The EGFP-AcPRMT1 fusion protein was distributed over the cytoplasm, but it was mainly localized in the nucleus of Acanthamoeba. Knock down of AcPRMT1 by synthetic siRNA with a complementary sequence failed to form mature cysts. These findings suggested that AcPRMT1 plays a critical role in the regulation of encystation of A. castellanii. The target gene of AcPRMT1 regulation and the detailed mechanisms need to be investigated by further studies.

Protein arginine methyltransferase 1 methylates SF2/ASF at arginine / 中国肿瘤生物治疗杂志

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.