title: A PTIP-PA1 subcomplex promotes transcription for IgH class switching independently from the associated MLL3/MLL4 methyltransferase complex.
abstract: Class switch recombination (CSR) diversifies antibodies for productive immune responses while maintaining stability of the B-cell genome. Transcription at the immunoglobulin heavy chain (Igh) locus targets CSR-associated DNA damage and is promoted by the BRCT domain-containing PTIP (Pax transactivation domain-interacting protein). Although PTIP is a unique component of the mixed-lineage leukemia 3 (MLL3)/MLL4 chromatin-modifying complex, the mechanisms for how PTIP promotes transcription remain unclear. Here we dissected the minimal structural requirements of PTIP and its different protein complexes using quantitative proteomics in primary lymphocytes. We found that PTIP functions in transcription and CSR separately from its association with the MLL3/MLL4 complex and from its localization to sites of DNA damage. We identified a tandem BRCT domain of PTIP that is sufficient for CSR and identified PA1 as its main functional protein partner. Collectively, we provide genetic and biochemical evidence that a PTIP-PA1 subcomplex functions independently from the MLL3/MLL4 complex to mediate transcription during CSR. These results further our understanding of how multifunctional chromatin-modifying complexes are organized by subcomplexes that harbor unique and distinct activities.
authors.affiliation: Chromatin Structure and Function Group, The Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen 2200, Denmark;
authors.forename: Linda M
authors.initials: LM
authors.lastname: Starnes
authors.affiliation: Chromatin Structure and Function Group, The Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen 2200, Denmark;
authors.forename: Dan
authors.initials: D
authors.lastname: Su
authors.affiliation: Chromatin Structure and Function Group, The Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen 2200, Denmark;
authors.forename: Laura M
authors.initials: LM
authors.lastname: Pikkupeura
authors.affiliation: Proteomics and Cell Signaling Group, The Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen 2200, Denmark;
authors.forename: Brian T
authors.initials: BT
authors.lastname: Weinert
authors.affiliation: Laboratory of Genome Integrity, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA;
authors.forename: Margarida A
authors.initials: MA
authors.lastname: Santos
authors.affiliation: Chromatin Structure and Function Group, The Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen 2200, Denmark;
authors.forename: Andreas
authors.initials: A
authors.lastname: Mund
authors.affiliation: Chromatin Structure and Function Group, The Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen 2200, Denmark;
authors.forename: Rebeca
authors.initials: R
authors.lastname: Soria
authors.affiliation: Adipocyte Biology and Gene Regulation Section, Laboratory of Endocrinology and Receptor Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA;
authors.forename: Young-Wook
authors.initials: YW
authors.lastname: Cho
authors.affiliation: Protein Production and Characterization Platform, The Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen 2200, Denmark;
authors.forename: Irina
authors.initials: I
authors.lastname: Pozdnyakova
authors.affiliation: Chromatin Structure and Function Group, The Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen 2200, Denmark;
authors.forename: Martina
authors.initials: M
authors.lastname: Kubec Højfeldt
authors.affiliation: Protein Production and Characterization Platform, The Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen 2200, Denmark;
authors.forename: Andrea
authors.initials: A
authors.lastname: Vala
authors.affiliation: Department of Physics, The George Washington University, Washington, DC 20052, USA;
authors.forename: Wenjing
authors.initials: W
authors.lastname: Yang
authors.affiliation: Protein Production and Characterization Platform, The Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen 2200, Denmark;
authors.forename: Blanca
authors.initials: B
authors.lastname: López-Méndez
authors.affiliation: Adipocyte Biology and Gene Regulation Section, Laboratory of Endocrinology and Receptor Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA;
authors.forename: Ji-Eun
authors.initials: JE
authors.lastname: Lee
authors.affiliation: Department of Physics, The George Washington University, Washington, DC 20052, USA;
authors.forename: Weiqun
authors.initials: W
authors.lastname: Peng
authors.affiliation: Developmental Immunology Group, Division of Molecular Hematology, Lund Stem Cell Center, Faculty of Medicine, Lund University, Lund 22184, Sweden;
authors.forename: Joan
authors.initials: J
authors.lastname: Yuan
authors.affiliation: Adipocyte Biology and Gene Regulation Section, Laboratory of Endocrinology and Receptor Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA;
authors.forename: Kai
authors.initials: K
authors.lastname: Ge
authors.affiliation: Protein Production and Characterization Platform, The Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen 2200, Denmark; Macromolecular Crystallography Group, The Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen 2200, Denmark.
authors.forename: Guillermo
authors.initials: G
authors.lastname: Montoya
authors.affiliation: Laboratory of Genome Integrity, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA;
authors.forename: André
authors.initials: A
authors.lastname: Nussenzweig
authors.affiliation: Proteomics and Cell Signaling Group, The Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen 2200, Denmark;
authors.forename: Chunaram
authors.initials: C
authors.lastname: Choudhary
authors.affiliation: Chromatin Structure and Function Group, The Novo Nordisk Foundation Center for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen 2200, Denmark;
authors.forename: Jeremy A
authors.initials: JA
authors.lastname: Daniel
mesh_terms: D002352:Carrier Proteins / Q000378:metabolism*; D004249:DNA Damage; D004268:DNA-Binding Proteins; D005786:Gene Expression Regulation / Q000276:immunology; D011495:Histone-Lysine N-Methyltransferase / Q000378:metabolism*; D017578:Immunoglobulin Class Switching / Q000235:genetics*; D007143:Immunoglobulin Heavy Chains / Q000235:genetics* / Q000276:immunology*; D015394:Molecular Structure; D009687:Nuclear Proteins / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D021381:Protein Transport
chemical_list: D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D007143:Immunoglobulin Heavy Chains; D009687:Nuclear Proteins; C412792:Paxip1 protein, mouse; D011495:Histone-Lysine N-Methyltransferase; C510652:Kmt2c protein, mouse; C516439:MLL4 protein, mouse
keywords: 53BP1; BRCT domains; DNA damage; PTIP; antigen receptor rearrangements; histone methylation