PRMT-5 converts monomethylarginines into symmetrical dimethylarginines in Caenorhabditis elegans

Glutathionylation Decreases Methyltransferase Activity of PRMT5 and Inhibits Cell Proliferation

Glutathionylation is an important posttranslational modification that protects proteins from further oxidative damage as well as influencing protein structure and activity. In the present study, we demonstrate that the cysteine-42 residue in protein arginine N-methyltransferase 5 (PRMT5) is glutathionylated in aged mice or in cells that have been exposed to oxidative stress. Deglutathionylation of this protein is catalyzed by glutaredoxin-1 (Grx1). Using mutagenesis and subsequent biochemical analyses, we show that glutathionylation decreased the binding affinity of PRMT5 with methylosome protein-50 (MEP50) and reduced the methyltransferase activity of PRMT5. Furthermore, overexpression of PRMT5-C42A mutant caused a significant increase in histone methylation in HEK293T and A549 cells and promoted cell growth, whereas overexpression of the PRMT5-C42D mutant, a mimic of glutathionylated PRMT5, inhibited cell proliferation. Taken together, our results demonstrate a new mechanism of regulation of PRMT5 methyltransferases activity and suggest that PRMT5 glutathionylation is partly responsible for reactive oxygen species-mediated cell growth inhibition.

Histone H4R3 symmetric di-methylation by Prmt5 protects against cardiac hypertrophy via regulation of Filip1L/β-catenin

BACKGROUND AND PURPOSE

Although histone lysine methylation has been extensively studied for their participation in pathological cardiac hypertrophy, the potential regulatory role of histone arginine methylation remains to be elucidated. The present study focused on H4R3 symmetric di-methylation (H4R3me2s) induced by protein arginine methyltransferase 5 (Prmt5), and explored its epigenetic regulation and underlying mechanisms in cardiomyocyte hypertrophy.

METHODS AND RESULTS

1. The expressions of Prmt5 and H4R3me2s were suppressed in cardiac hypertrophy models in vivo and in vitro; 2. Prmt5 silencing or its inhibitor EPZ, or knockdown of cooperator of Prmt5 (Copr5) to disrupt H4R3me2s, facilitated cardiomyocyte hypertrophy, whereas overexpression of wild type Prmt5 rather than the inactive mutant protected cardiomyocytes against hypertrophy; 3. ChIP-sequence analysis identified Filip1L as a target gene of Prmt5-induced H4R3me2s; 4. Knockdown or inhibition of Prmt5 impaired Filip1L transcription and subsequently prevented β-catenin degradation, thus augmenting cardiomyocyte hypertrophy.

CONCLUSIONS

The present study reveals that Prmt5-induced H4R3me2s ameliorates cardiomyocyte hypertrophy by transcriptional upregulation of Filip1L and subsequent enhancement of β-catenin degradation. Deficiency of Prmt5 and the resulting suppression of H4R3me2s might facilitate the development of pathological cardiac hypertrophy. Prmt5 might serve as a key epigenetic regulator in pathological cardiac hypertrophy.

The N-terminal sequence of murine PRMT5 variant 2 is required for Hsp70 interaction and CHIP ligase-mediated degradation

Protein arginine methyltransferase PRMT5 synthesizes the symmetric dimethylarginine in nuclear and cytoplasmic proteins such as histone H2A, H4 and several non-histone proteins that are required for a variety of biological processes. Currently, two splice variants (v1 and v2) of murine PRMT5 have been deposited in the NCBI sequence database, in which PRMT5-v1 and -v2 contain different 33 and 16 amino acids at the N-terminal sequences, respectively. Here we showed that murine PRMT5-v1 is stable, but PRMT5-v2 is constantly degraded through both the ubiquitin proteasome system (UPS) and the autophagic-lysosomal pathway (ALP) in an N-terminal sequence-dependent manner. Furthermore, inhibition of UPS and ALP elevated the stability of PRMT5-v2 that made it localized in the nucleus and the cytoplasm. In addition, PRMT5-v2 exhibited the enzyme activity to catalyze histone H2A and H4 methylation. Notably, we found that the heat shock protein (Hsp) 70 specially recognizes the N-terminal sequence of PRMT5-v2 and the carboxyl terminus of Hsp70-interacting protein (CHIP) is required for poly-ubiquitination and the degradation of PRMT5-v2. These results suggest that Hsp70/CHIP chaperone-mediated protein degradation system is crucial in the regulation of PRMT5-v2 turnover, which has the potential to balance the symmetrical arginine dimethylation in cells.

Emerging impacts of biological methylation on genetic information

The central dogma of molecular biology explains the fundamental flow of genetic information for life. Although genome sequence (DNA) itself is a static chemical signature, it includes multiple layers of information composed of mRNA, tRNA, rRNA and small RNAs, all of which are involved in protein synthesis and is passing from parents to offspring via DNA. Methylation is a biologically important modification, because DNA, RNAs and proteins, components of the central dogma, are methylated by a set of methyltransferases. Recent works focused on understanding a variety of biological methylation have shed light on new regulation of cellular functions. In this review, we briefly discuss some of those recent findings of methylation, including DNA, RNAs and proteins.

The GATA transcription factor ELT-2 modulates both the expression and methyltransferase activity of PRMT-1 in Caenorhabditis elegans

Protein arginine methyltransferase 1 (PRMT1) catalyzes asymmetric arginine dimethylation of cellular proteins and thus modulates various biological processes, including gene regulation, RNA metabolism, cell signaling and DNA repair. Since prmt-1 null mutant completely abolishes asymmetric dimethylarginine in C. elegans, PRMT-1 is thought to play a crucial role in determining levels of asymmetric arginine dimethylation. However, the mechanism underlying the regulation of PRMT-1 activity remains largely unknown. Here, we explored for transcription factors that induce the expression of PRMT-1 by an RNAi screen using transgenic C. elegans harbouring prmt-1 promoter upstream of gfp. Of 529 clones, we identify a GATA transcription factor elt-2 as a positive regulator of Pprmt-1:: gfp expression and show that elt-2 RNAi decreases endogenous PRMT-1 expression at mRNA and protein levels. Nevertheless, surprisingly arginine methylation levels are increased when elt-2 is silenced, implying that erythroid-like transcription factor (ELT)-2 may also have ability to inhibit methyltransferase activity of PRMT-1. Supporting this idea, GST pull-down and co-immunoprecipitation assays demonstrate the interaction between ELT-2 and PRMT-1. Furthermore, we find that ELT-2 interferes with PRMT-1-induced arginine methylation in a dose-dependent manner. Collectively, our results illustrate the two modes of PRMT-1 regulation, which could determine the levels of asymmetric arginine dimethylation in C. elegans.

Gestational changes in PRMT1 expression of murine placentas

INTRODUCTION

In mammals, the placenta is an organ that is required to maintain the development of fetus during pregnancy. Although the proper formation of placenta is in part regulated by the post-translational modifications of proteins, little is known regarding protein arginine methylation during placental development. Here, we characterized developmental expression of protein arginine methyltransferase 1 (PRMT1) in mouse placentas.

METHODS

Expression levels of PRMT1 mRNA and protein in placentas were investigated using the real-time quantitative PCR and Western blot, respectively. Next, the localization of PRMT1 was determined by immunohistochemistry and immunofluorescence analyses. In addition, the levels of methylarginines of placental proteins were quantified using liquid chromatography-tandem mass spectrometry (LC-MS/MS).

RESULTS

PRMT1 mRNA and its protein were expressed at highest levels in mid-gestation stages, and their expression showed stepwise decrease in the late gestation. At embryonic (E) day 9, PRMT1 was observed in several different trophoblast cell (TC) subtypes. Furthermore, PRMT1 was mainly expressed in the labyrinth zone of TCs at E13. Finally, total methylarginines of proteins were significantly reduced in late gestation of placentas compared with mid-gestation stages.

DISCUSSION

In this study, we found developmental changes in the placental expression of PRMT1 and in protein arginine methylation status during pregnancy. These findings provide fundamental information regarding placental PRMT1-mediated arginine methylation during the development.

Asymmetric Arginine Dimethylation Modulates Mitochondrial Energy Metabolism and Homeostasis in Caenorhabditis elegans

Protein arginine methyltransferase 1 (PRMT-1) catalyzes asymmetric arginine dimethylation on cellular proteins and modulates various aspects of biological processes, such as signal transduction, DNA repair, and transcriptional regulation. We have previously reported that the null mutant of prmt-1 in Caenorhabditis elegans exhibits a slightly shortened life span, but the physiological significance of PRMT-1 remains largely unclear. Here we explored the role of PRMT-1 in mitochondrial function as hinted by a two-dimensional Western blot-based proteomic study. Subcellular fractionation followed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis showed that PRMT-1 is almost entirely responsible for asymmetric arginine dimethylation on mitochondrial proteins. Importantly, isolated mitochondria from prmt-1 mutants represent compromised ATP synthesis in vitro, and whole-worm respiration in prmt-1 mutants is decreased in vivo Transgenic rescue experiments demonstrate that PRMT-1-dependent asymmetric arginine dimethylation is required to prevent mitochondrial reactive oxygen species (ROS) production, which consequently causes the activation of the mitochondrial unfolded-protein response. Furthermore, the loss of enzymatic activity of prmt-1 induces food avoidance behavior due to mitochondrial dysfunction, but treatment with the antioxidant N-acetylcysteine significantly ameliorates this phenotype. These findings add a new layer of complexity to the posttranslational regulation of mitochondrial function and provide clues for understanding the physiological roles of PRMT-1 in multicellular organisms.