title: Evolutionarily divergent type II protein arginine methyltransferase in Trypanosoma brucei.
abstract: Protein arginine methylation is a posttranslational modification that impacts cellular functions, such as RNA processing, transcription, DNA repair, and signal transduction. The majority of our knowledge regarding arginine methylation derives from studies of yeast and mammals. Here, we describe a protein arginine N-methyltransferase (PRMT), TbPRMT5, from the early-branching eukaryote Trypanosoma brucei. TbPRMT5 shares the greatest sequence similarity with PRMT5 and Skb1 type II enzymes from humans and Schizosaccharomyces pombe, respectively, although it is significantly divergent at the amino acid level from its mammalian and yeast counterparts. Recombinant TbPRMT5 displays broad substrate specificity in vitro, including methylation of a mitochondrial-gene-regulatory protein, RBP16. TbPRMT5 catalyzes the formation of omega-N(G)-monomethylarginine and symmetric omega-N(G),N(G')-dimethylarginine and does not require trypanosome cofactors for this activity. These data establish that type II PRMTs evolved early in the eukaryotic lineage. In vivo, TbPRMT5 is constitutively expressed in the bloodstream form and procyclic-form (insect host) life stages of the parasite and localizes to the cytoplasm. Genetic disruption via RNA interference in procyclic-form trypanosomes indicates that TbPRMT5 is not essential for growth in this life cycle stage. TbPRMT5-TAP ectopically expressed in procyclic-form trypanosomes is present in high-molecular-weight complexes and associates with an RG domain-containing DEAD box protein related to yeast Ded1 and two kinetoplastid-specific proteins. Thus, TbPRMT5 is likely to be involved in novel methylation-regulated functions in trypanosomes, some of which may include RNA processing and/or translation.
authors.affiliation: Department of Microbiology and Immunology and Witebsky Center for Microbial Pathogenesis and Immunology, State University of New York School of Medicine, Buffalo, New York 14214, USA.
authors.forename: Deborah A
authors.initials: DA
authors.lastname: Pasternack
authors.forename: Joyce
authors.initials: J
authors.lastname: Sayegh
authors.forename: Steven
authors.initials: S
authors.lastname: Clarke
authors.forename: Laurie K
authors.initials: LK
authors.lastname: Read
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002384:Catalysis; D053487:DEAD-box RNA Helicases / Q000378:metabolism; D019143:Evolution, Molecular; D017125:Genes, Protozoan; D008745:Methylation; D008969:Molecular Sequence Data; D010802:Phylogeny; D011484:Protein-Arginine N-Methyltransferases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015800:Protozoan Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics; D013379:Substrate Specificity; D014346:Trypanosoma brucei brucei / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D019323:omega-N-Methylarginine / Q000096:biosynthesis
chemical_list: D015800:Protozoan Proteins; D011994:Recombinant Proteins; D019323:omega-N-Methylarginine; D011484:Protein-Arginine N-Methyltransferases; D053487:DEAD-box RNA Helicases