Toxoplasma gondii Arginine Methyltransferase 1 (PRMT1) Is Necessary for Centrosome Dynamics during Tachyzoite Cell Division

Abstract

The arginine methyltransferase family (PRMT) has been implicated in a variety of cellular processes, including signal transduction, epigenetic regulation, and DNA repair pathways. PRMT1 is thought to be responsible for the majority of PRMT activity in Toxoplasma gondii, but its exact function is unknown. To further define the biological function of the PRMT family, we generated T. gondii mutants lacking PRMT1 (Δprmt1) by deletion of the PRMT1 gene. Δprmt1 parasites exhibit morphological defects during cell division and grow slowly, and this phenotype reverses in the Δprmt::PRMT1mRFP complemented strain. Tagged PRMT1 localizes primarily in the cytoplasm with enrichment at the pericentriolar material, and the strain lacking PRMT1 is unable to segregate progeny accurately. Unlike wild-type and complemented parasites, Δprmt1 parasites have abnormal daughter buds, perturbed centrosome stoichiometry, and loss of synchronous replication. Whole-genome expression profiling demonstrated differences in expression of cell-cycle-regulated genes in the Δprmt1 strain relative to the complemented Δprmt1::PRMT1mRFP and parental wild-type strains, but these changes do not correlate with a specific block in cell cycle. Although PRMT1’s primary biological function was previously proposed to be methylation of histones, our studies suggest that PRMT1 plays an important role within the centrosome to ensure the proper replication of the parasite.

Novel insights into the composition and function of theToxoplasmaIMC sutures

“…Surprisingly, Δisc3 parasites are completely avirulent in vivo , as mice were completely resistant to dosages of up to 10 6 knockout parasites, whereas the type I parental strain has an LD 100 = 1 in mice. This is in contrast to various other type I knockouts that have fitness defects and produce significantly smaller plaques in vitro yet are still able to kill mice with low doses of parasites, albeit sometimes with a delay in the time of death (Blume et al ., ; Shen, Buguliskis, Lee, & Sibley, ; Hammoudi et al ., ; El Bissati et al ., ; Pszenny et al , ). This discrepancy between the in vitro and in vivo phenotypes of Δisc3 parasites may reflect a reduced capacity of these knockouts to establish a productive infection upon intraperitoneal injection into mice.…”

Towards a molecular architecture of the centrosome in Toxoplasma gondii

“…Surprisingly, an atypical kinase called MAPK‐Like and an arginine methyltransferase 1 were found associated with the PCM in T. gondii (El Bissati et al, ; Suvorova et al, ). Functional analysis revealed that MAPK‐like is required for proper daughter cell budding and mitosis while the arginine methyltransferase 1 PRMT1 is involved in the budding process and maintenance of centrosome stoichiometry (El Bissati et al, ; Suvorova et al, ). Finally, TgCDPK7 is required for centrosomal positioning and integrity (Morlon‐Guyot et al, ) (Figure B).…”

Comparative Monomethylarginine Proteomics Suggests that Protein Arginine Methyltransferase 1 (PRMT1) is a Significant Contributor to Arginine Monomethylation in Toxoplasma gondii

“…Changes in transcription occur during life cycle transitions (26) and PTMs are important regulators of the T. gondii cell cycle (27). In previous work, we identified multiple monomethylated arginine residues on T. gondii histones (28,29). T. gondii, encodes five PRMTs, four of which are predicted to be type I PRMTs and one that is predicted to be a type II enzyme, based on sequence similarity to human homologues (supplemental Table S1).…”

“…T. gondii, encodes five PRMTs, four of which are predicted to be type I PRMTs and one that is predicted to be a type II enzyme, based on sequence similarity to human homologues (supplemental Table S1). Two of the type I PRMTs, TgPRMT1 and TgPRMT4, possess protein arginine methyltransferase activity and modify histones (29,30). Tg-PRMT4 localizes to the nucleus of the parasite where it has been implicated in gene regulation and parasite development (30).…”

“…TgPRMT1, on the other hand, localizes primarily to the cytosol and pericentriolar regions and ensures correct segre- 1 The abbreviations used are: PRMTs, protein arginine methyltransferases; ApiAP2, Apicomplexan Apetala 2 transcription factors; Arg, arginine (R); cdpk, calcium dependent protein kinase; CARM1, coactivator-associated arginine methyltransferase 1; Cys, cysteine (C); DUF, domain of unknown function; EXTRA, extracellular; FDR, false discovery rate; GO, Gene Ontology; GAR, glycine-arginine; H3R2me2, histone 3 dimethyl arginine 2; H4R3me2, histone 4 dimethyl arginine 3; HFF, human foreskin fibroblasts; JMJD6, jumonji domain-containing protein 6; KEGG, Kyoto Encyclopedia of Genes and Genomes; Lys, lysine (L); MGF, mascot generic format; Met, methionine (M); MMA, monomethyl arginine; ADMA, NG-NG-asymmetric dimethylarginine; SDMA, omega NG-NG-symmetric dimethylarginine; PADIs, peptidyl arginine deiminases; PBS, phosphate buffered saline; PTM, post translational modification; PRMT1COMP, PRMT1 complemented T. gondii strain; PRMT1KO, PRMT1 knockout T. gondii strain; RBD, RNA binding domain; RBP, RNA binding proteins; RRM, RNA Recognition Motif; STY, serine threonine tyrosine; SPT6, suppressor of Ty 6; Trp, tryptophan (W); Tyr, tyrosine (Y); WT, wild type. gation of daughter cells during parasite replication (29). Like human PRMT1 (20), TgPRMT1 is not essential to viability, however deletion of TgPRMT1 results in loss of synchronous replication and a disrupted cell cycle, along with changes in gene expression (29).…”