title: SUMOylation of the polycomb group protein L3MBTL2 facilitates repression of its target genes.
abstract: Lethal(3) malignant brain tumour like 2 (L3MBTL2) is an integral component of the polycomb repressive complex 1.6 (PRC1.6) and has been implicated in transcriptional repression and chromatin compaction. Here, we show that L3MBTL2 is modified by SUMO2/3 at lysine residues 675 and 700 close to the C-terminus. SUMOylation of L3MBTL2 neither affected its repressive activity in reporter gene assays nor it's binding to histone tails in vitro. In order to analyse whether SUMOylation affects binding of L3MBTL2 to chromatin, we performed ChIP-Seq analysis with chromatin of wild-type HEK293 cells and with chromatin of HEK293 cells stably expressing either FLAG-tagged SUMOylation-competent or SUMOylation-defective L3MBTL2. Wild-type FLAG-L3MBTL2 and the SUMOylation-defective FLAG-L3MBTL2 K675/700R mutant essentially occupied the same sites as endogenous L3MBTL2 suggesting that SUMOylation of L3MBTL2 does not affect chromatin binding. However, a subset of L3MBTL2-target genes, particularly those with low L3MBTL2 occupancy including pro-inflammatory genes, was de-repressed in cells expressing the FLAG-L3MBTL2 K675/700R mutant. Finally, we provide evidence that SUMOylation of L3MBTL2 facilitates repression of these PRC1.6-target genes by balancing the local H2Aub1 levels established by the ubiquitinating enzyme RING2 and the de-ubiquitinating PR-DUB complex.
authors.affiliation: Institute of Molecular Biology and Tumor Research, Philipps-University, Emil-Mannkopff-Str. 2, D-35032 Marburg and Helmholtz Centre for Infection Research (HZI), Inhoffenstraße 7, D-38124 Braunschweig, Germany.
authors.forename: Christina
authors.initials: C
authors.lastname: Stielow
authors.forename: Bastian
authors.initials: B
authors.lastname: Stielow
authors.forename: Florian
authors.initials: F
authors.lastname: Finkernagel
authors.forename: Maren
authors.initials: M
authors.lastname: Scharfe
authors.forename: Michael
authors.initials: M
authors.lastname: Jarek
authors.forename: Guntram
authors.initials: G
authors.lastname: Suske
mesh_terms: D001665:Binding Sites; D050701:E2F6 Transcription Factor / Q000378:metabolism; D005786:Gene Expression Regulation; D015894:Genome, Human; D057809:HEK293 Cells; D006657:Histones / Q000378:metabolism; D006801:Humans; D008239:Lysine / Q000378:metabolism; D009687:Nuclear Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D012097:Repressor Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D058207:Sumoylation; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism
chemical_list: D050701:E2F6 Transcription Factor; D006657:Histones; C439764:L3MBTL2 protein, human; D009687:Nuclear Proteins; D012097:Repressor Proteins; D014157:Transcription Factors; D044767:Ubiquitin-Protein Ligases; D008239:Lysine