title: Clr4 specificity and catalytic activity beyond H3K9 methylation.
abstract: In fission yeast, the catalytic activity of the protein lysine methyltransferase (PKMT) Clr4, the sole homolog of the mammalian SUV39H1 and SUV39H2 enzymes, majorly contributes to the formation of heterochromatin. The enzyme introduces histone 3 lysine 9 (H3K9) di- and tri-methylation, a central heterochromatic histone modification, and later it was also found to methylate the Mlo3 protein, which has a role in heterochromatin formation as well. Herein, we have investigated the substrate specificity of Clr4 using custom made mutational scanning peptide arrays. Our data show, that Clr4 recognizes an RK core motif, showing high preference for R8. In addition, it exhibits specific contacts at the S10, T11, G12 and G13 positions of the H3 peptide recognizing an R-K-SKRT-TCS-G sequence. Based on the specificity profile and in vitro methyltransferase assay targeted searches, 11 putative methylation sites in S. pombe proteins were identified from reported Clr4 interacting proteins including Mlo3. Peptide methylation was observed on Mlo3 and 7 novel target sites with strongest methylation signals on Spbc28F2.11 (HMG box-containing protein) at lysine 292 and Hrp3 (Chromodomain ATP-dep DNA helicase) at lysine 89. These data suggest that Clr4 has additional methylation substrates and it will be important to study the biological function of these novel methylation events. Furthermore, the specificity profile of Clr4 has been used to develop a quantitative method to compare and cluster specificity profiles of PKMTs. It shows that the specificity profile of Clr4 is most similar to that of the SUV39H2 enzyme, one of its human homologs. This approach will be helpful in the comparison of the recognition profiles of other families of PKMTs as well.
authors.affiliation: Institute of Biochemistry, Faculty of Chemistry, University Stuttgart, Stuttgart, Germany.
authors.forename: Denis
authors.initials: D
authors.lastname: Kusevic
authors.affiliation: Institute of Biochemistry, Faculty of Chemistry, University Stuttgart, Stuttgart, Germany.
authors.forename: Srikanth
authors.initials: S
authors.lastname: Kudithipudi
authors.affiliation: Department of Cell Biology, Howard Hughes Medical Institute, Harvard Medical School, Boston, United States.
authors.forename: Nahid
authors.initials: N
authors.lastname: Iglesias
authors.affiliation: Department of Cell Biology, Howard Hughes Medical Institute, Harvard Medical School, Boston, United States.
authors.forename: Danesh
authors.initials: D
authors.lastname: Moazed
authors.affiliation: Institute of Biochemistry, Faculty of Chemistry, University Stuttgart, Stuttgart, Germany. Electronic address: albert.jeltsch@ibc.uni-stuttgart.de.
authors.forename: Albert
authors.initials: A
authors.lastname: Jeltsch
mesh_terms: D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D011495:Histone-Lysine N-Methyltransferase; D006657:Histones / Q000378:metabolism*; D008239:Lysine / Q000378:metabolism*; D008745:Methylation; D008780:Methyltransferases / Q000235:genetics / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D012568:Schizosaccharomyces / Q000201:enzymology / Q000378:metabolism*; D029702:Schizosaccharomyces pombe Proteins / Q000235:genetics / Q000378:metabolism*; D013379:Substrate Specificity
chemical_list: D018797:Cell Cycle Proteins; D006657:Histones; D029702:Schizosaccharomyces pombe Proteins; D008780:Methyltransferases; D011495:Histone-Lysine N-Methyltransferase; C112744:clr4 protein, S pombe; D008239:Lysine
keywords: Enzyme specificity; Lysine methylation; Post-translational modifications; Protein methylation