Dataset Information

Proteomics Profiling of Arginine Methylation Defines PRMT5 Substarate Specificity

ABSTRACT: Protein arginine methyltransferases (PRMTs) catalyze arginine methylation, an abundant post-translational modification occurring on both chromatin-bound and cytoplasmic proteins. Growing evidence supports the involvement of PRMT5, the major Type II PRMT, in pro-survival and differentiation pathways, important during development and to promote tumorigenesis. Thus, PRMT5 emerges as an attractive drug target and inhibitors are currently in clinical trials for cancer therapy. However, the knowledge of PRMT5 non-histone substrates is still limited, as are the dynamic changes in methylation levels upon its inhibition. Here, we employed a newly established pipeline coupling SILAC with methyl-peptides immuno-enrichment to globally profile arginine methylation following PRMT5 inhibition by GSK591 and adopted the heavy-methyl SILAC as orthogonal validation method to reduce false discovery rate. Then, in vitro methylation assays on a set of PRMT5 targets provided novel mechanistic insights into its strict preference to methylate arginine sandwiched between two neighbouring glycines (GRG). In conclusion, we identified novel PRMT5 substrates, thus providing the first proof of concept of the in vivo efficacy of PRMT5 inhibitor that impacts on arginine methylation beyond histones.

INSTRUMENT(S): Q Exactive

ORGANISM(S): Homo Sapiens (human)

TISSUE(S): Hela Cell

DISEASE(S): Cervix Carcinoma

SUBMITTER: alessandro cuomo

LAB HEAD: Tiziana Bonaldi

PROVIDER: PXD009070 | Pride | 2019-04-10

REPOSITORIES: Pride

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			Action	DRS
	HF170324_DM_EG_GSK591_HeLa_Fwd_Mono01.raw	Raw
	HF170324_DM_EG_GSK591_HeLa_Fwd_Mono02.raw	Raw
	HF170324_DM_EG_GSK591_HeLa_Fwd_Mono03.raw	Raw
	HF170324_DM_EG_GSK591_HeLa_Fwd_Mono04.raw	Raw
	HF170324_DM_EG_GSK591_HeLa_Fwd_Mono05.raw	Raw

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Proteomics profiling of arginine methylation defines PRMT5 substrate specificity.

Musiani Daniele D Bok Jabez J Massignani Enrico E Wu Liling L Tabaglio Tommaso T Ippolito Marica Rosaria MR Cuomo Alessandro A Ozbek Umut U Zorgati Habiba H Ghoshdastider Umesh U Robinson Robert C RC Guccione Ernesto E Bonaldi Tiziana T

Science signaling 20190402 575

Protein arginine methyltransferases (PRMTs) catalyze arginine methylation on both chromatin-bound and cytoplasmic proteins. Accumulating evidence supports the involvement of PRMT5, the major type II PRMT, in cell survival and differentiation pathways that are important during development and in tumorigenesis. PRMT5 is an attractive drug target in various cancers, and inhibitors are currently in oncological clinical trials. Nonetheless, given the complex biology of PRMT5 and its multiple nonhisto ...[more]

PMID: 30940768

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Project description:PRMT5 is the major enzyme that catalyzes the symmetric dimethylation of arginine (sDMA) in mammalian cells. Its activity is crucial for many biological processes including transcriptional regulation, mRNA processing, as well as DNA damage and repair. However, the protein substrates identified for PRMT5 have yet been limited in numbers, hindering the understanding of PRMT5 functions in normal as well as diseased cells. Herein we developed an optimized strategy for proteomic profiling of cellular sDMA and apply it to the discovery of novel PRMT5 substrates. Our results show that a combination of proteolytic digestion by the metalloprotease ulilysin and using electron-transfer dissociation with supplemental activation as the mass spectrometry method significantly increased sDMA site identification and localization after immuno-affinity enrichment. By employing SILAC-based differential quantitative proteomic approach and a PRMT5 specific inhibitor, we identified 325 sDMA sites being regulated by PRMT5, 220 being novel sites, which greatly expanded the number of PRMT5 substrates. Biochemical studies confirmed the newly discovered PRMT5 substrate, Plasminogen activator inhibitor 1 RNA-binding protein (SERBP1) and revealed that the RGG/RG motif in the central region of SERBP1 contains both PRMT5-catalyzed sDMA and Type I PRMT-catalyzed asymmetric dimethylation of arginine (aDMA). Unexpectedly, using the optimized methylarginine profiling strategy, we also discovered arginine trimethylation, a previously unknown type of modification, on the central RGG/RG region of SERBP1. By mutational studies we demonstrated that the trimethyl modification on R172 of SERBP1 regulates its recruitment to stress granule (SG) under oxidative stress, indicating a functional role of arginine trimethylation in the cell. Overall, the optimized profiling strategy not only enabled the identification of extensive, non-overlapping sDMA sites and novel PRMT5 substrates, but also revealed a potentially important new PTM, arginine trimethylation. The work lays the foundation for further investigations on the functional interplay of different methylation modifications on arginines, especially in the heavily methylated RGG/RG motif of many RNA-binding proteins.

Project description:Protein methylation has been implicated in many important biological contexts including signaling, metabolism, and transcriptional control. Despite the importance of this post- translational modification, the global analysis of protein methylation by mass spectrometry-based proteomics has not been extensively studied due to the lack of robust, well-characterized techniques for methyl-peptidemethyl peptide enrichment. Here, to better investigate protein methylation, we optimized and compared two methods for methyl-peptidemethyl peptide enrichment: immunoaffinity purification (IAP) and high pH strong cation exchange (SCX). Comparison of these methods revealed that they are largely orthogonal for monomethyl arginine (MMA), suggesting that the usage of both techniques is required to provide a global view of protein methylation. Using both IAP and SCX, we investigated changes in protein methylation downstream of protein arginine methyltransferase 1 (PRMT1). Together, these techniques allowed us to quantify over ~1,000 arginine methylation sites on 407 proteins. Of these methylation sites, PRMT1 knockdown resulted in significant changes to 110 arginine methylation sites on 59 proteins. In contrast, zero lysine methylation sites were significantly changed upon PRMT1 knockdown. In PRMT1 knockdown cells, 24 MMA sites exhibited both significant downregulation (ie, putative PRMT1-mediated MMA targets) and 63 significant upregulation (ie, putative PRMT1-mediated ADMA targets). PRMT1 knockdown induced significant changes in asymmetric dimethyl arginine (ADMA), consistent with being PRMT1 targets. Additionally, We also observed that PRMT1 knockdown induced significant increases in symmetric dimethyl arginine (SDMA) methylation, suggesting that loss of PRMT1 activity allows scavenging of PRMT1 substrates by Type II PRMTs. Analysis of the subcellular localization and protein function of the significantly changing methyl-proteins revealed that the majority of PRMT1 substrates are localized to the nucleus and involved in RNA and DNA binding. Taken together, our results suggest that deep protein methylation profiling by mass spectrometry requires orthogonal enrichment techniques, identify novel PRMT1 methylation targets, and highlight in order to understand the dynamic interplay between methyltransferases in mammalian cells.