Regulation of PRMT1 by multiple phosphorylations

Protein arginine methyltransferases (PRMTs) have emerged as important regulators of protein functions in various cellular processes including signal transduction, RNA processing, DNA repair, and transcription. They exert their effects by catalyzing mono- or dimethylation of guanidine nitrogen atoms of arginine residues in proteins. PRMT1 is the predominant type I methyltransferase that generates approx. 85% of all cellular monomethyl- and asymmetrical dimethylarginines and is often dysregulated in human diseases including cancer. Its essential biological roles are supported by the early embryonic lethality observed for PRMT1-defficient mice. Despite recent progress in identification of PRMT1 substrates and understanding of the structural bases of its enzymology, the regulation of PRMT1 specific functions remains largely unknown. In this project, we aim to address the regulation of PRMT1 methyltransferase activity in a cell and to clarify molecular mechanisms of this regulation. Our preliminary studies revealed an inducible phosphorylation of human PRMT1 at several amino acid residues. To the best of our knowledge, this is the first evidence for posttranslational modification of the PRMT1 protein. The structural analysis of phosphorylated regions in PRMT1 allowed us to hypothesize that multiple phosphorylations of PRMT1 may regulate its enzymatic activity by modulating catalysis of the methyl group transfer, cofactor and substrate binding. The proposed mechanisms of the PRMT1 regulation will be investigated in biochemical, structural and functional studies. We also plan to investigate how the phosphorylation of PRMT1 affects its co-regulator function in transcription. In order to understand the physiological and possible pathological significance of the PRMT1 regulation by this posttranslational modification, the phosphorylation status of PRMT1 will be examined in normal and cancer cells.

Arginine methylation is a common posttranslational modification of proteins implicated in various cellular processes, including epigenetic regulation of transcription, cell signalling, DNA repair, and pre-mRNA processing. Although a number of arginine methyltransferases (PRMTs) and related substrates are identified, especially in the last decade, the physiological and pathological roles of different PRMTs remain mostly unclear. It is also little known about the cellular control of methyltransferases and their mechanisms of regulation. In a study supported by the FWF we could identify the major type I PRMT1 as an integral part of inflammation-relevant signalling. Consequently, we studied in great details the functional role and regulation of PRMT1 in the context of inflammatory responses. Our published findings reveal that PRMT1 functions not only as a classical co-regulator of inflammatory genes, via methylation of histones, but also affects the activity of NF-?B by modifying this transcription factor. We describe a previously unidentified posttranslational modification of NF-?B, namely asymmetric arginine dimethylation, and unveil a unique inhibitory mechanism controlling TNFa/NF-?B signalling. Our research also reveals the phosphorylation at multiple sites and regulation of PRMT1 by inflammation-associated and oncogenic kinases. By applying various structural and biochemical methodologies, we elucidated how the phosphorylation of individual residues regulates the methyltransferase activity of PRMT1 and defined the relevant molecular mechanisms. In summary, our results contribute to a better understanding of PRMT1 and NF-?B functions in inflammation and dissect new mechanistic details of their regulation both at the cellular and molecular levels. These provide a potentially useful theoretical basis for the development of more specific pharmaceutical and diagnostic approaches relevant to inflammation.