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      A Newly Uncovered Group of Distantly Related Lysine Methyltransferases Preferentially Interact with Molecular Chaperones to Regulate Their Activity

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          Methylation is a post-translational modification that can affect numerous features of proteins, notably cellular localization, turnover, activity, and molecular interactions. Recent genome-wide analyses have considerably extended the list of human genes encoding putative methyltransferases. Studies on protein methyltransferases have revealed that the regulatory function of methylation is not limited to epigenetics, with many non-histone substrates now being discovered. We present here our findings on a novel family of distantly related putative methyltransferases. Affinity purification coupled to mass spectrometry shows a marked preference for these proteins to associate with various chaperones. Based on the spectral data, we were able to identify methylation sites in substrates, notably trimethylation of K135 of KIN/Kin17, K561 of HSPA8/Hsc70 as well as corresponding lysine residues in other Hsp70 isoforms, and K315 of VCP/p97. All modification sites were subsequently confirmed in vitro. In the case of VCP, methylation by METTL21D was stimulated by the addition of the UBX cofactor ASPSCR1, which we show directly interacts with the methyltransferase. This stimulatory effect was lost when we used VCP mutants (R155H, R159G, and R191Q) known to cause Inclusion Body Myopathy with Paget's disease of bone and Fronto-temporal Dementia (IBMPFD) and/or familial Amyotrophic Lateral Sclerosis (ALS). Lysine 315 falls in proximity to the Walker B motif of VCP's first ATPase/D1 domain. Our results indicate that methylation of this site negatively impacts its ATPase activity. Overall, this report uncovers a new role for protein methylation as a regulatory pathway for molecular chaperones and defines a novel regulatory mechanism for the chaperone VCP, whose deregulation is causative of degenerative neuromuscular diseases.

          Author Summary

          Methylation, or transfer of a single or multiple methyl groups (CH 3), is one of many post-translational modifications that occur on proteins. Such modifications can, in turn, affect numerous aspects of a protein, notably cellular localization, turnover, activity, and molecular interactions. In addition to post-translational modifications, the structural organization of a protein or protein complex can also have a significant impact on its function and stability. A group of factors known as “molecular chaperones” aid newly synthesized proteins in reaching their native conformation or alternating between physiologically relevant states. We present here a new family of factors that promote methylation of chaperones and show that, at least in one case, this modification translates into a modulation in the activity of the substrate chaperone. Our results not only characterize the function of previously unknown gene products, uncover a new role for protein methylation as a regulatory pathway for chaperones, and define a novel regulatory mechanism for the chaperone VCP, whose deregulation is causative of neuromuscular diseases, but also suggest the existence of a post-translational modification code that regulates molecular chaperones. Further decrypting this “chaperone code” will help understanding how the functional organization of the proteome is orchestrated.

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          Most cited references 65

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                Author and article information

                Role: Editor
                PLoS Genet
                PLoS Genet
                PLoS Genetics
                Public Library of Science (San Francisco, USA )
                January 2013
                January 2013
                17 January 2013
                : 9
                : 1
                [1 ]Institut de Recherches Cliniques de Montréal (IRCM), Montréal, Québec, Canada
                [2 ]McGill Centre for Bioinformatics and School of Computer Science, McGill University, Montréal, Québec, Canada
                [3 ]Department of Biochemistry, Université de Montréal, Montréal, Québec, Canada
                Stanford University School of Medicine, United States of America
                Author notes

                The authors have declared that no competing interests exist.

                Conceived and designed the experiments: PC BC. Performed the experiments: PC. Analyzed the data: PC ML-A DF MB BC. Wrote the paper: PC ML-A DF MB BC.


                This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

                Page count
                Pages: 13
                This work has been funded by the Canadian Institutes of Health Research (CIHR, grant MOP-82851, The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
                Research Article



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