title: RNF168 promotes noncanonical K27 ubiquitination to signal DNA damage.
abstract: Ubiquitination regulates numerous cellular processes by generating a versatile communication system based on eight structurally and functionally different chains linked through distinct residues. Except for K48 and K63, the biological relevance of different linkages is largely unclear. Here, we show that RNF168 ubiquitin ligase promotes noncanonical K27-linked ubiquitination both in vivo and in vitro. We demonstrate that residue K27 of ubiquitin (UbK27) is required for RNF168-dependent chromatin ubiquitination, by targeting histones H2A/H2A.X, and that it is the major ubiquitin-based modification marking chromatin upon DNA damage. Indeed, UbK27 is strictly required for the proper activation of the DNA damage response (DDR) and is directly recognized by crucial DDR mediators, namely 53BP1, Rap80, RNF168, and RNF169. Mutation of UbK27 has dramatic consequences on DDR activation, preventing the recruitment of 53BP1 and BRCA1 to DDR foci. Similarly to the DDR, atypical ubiquitin chains could play unanticipated roles in other crucial ubiquitin-mediated biological processes.
authors.affiliation: Department of Pharmaceutical Sciences, University of Piemonte Orientale, via Bovio 2, 28100 Novara, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Gatti
authors.affiliation: Department of Pharmaceutical Sciences, University of Piemonte Orientale, via Bovio 2, 28100 Novara, Italy.
authors.forename: Sabrina
authors.initials: S
authors.lastname: Pinato
authors.affiliation: Department of Biology, Institute of Molecular Systems Biology, Eidgenössische Technische Hochschule Zurich (ETHZ), 8093 Zurich, Switzerland.
authors.forename: Alessio
authors.initials: A
authors.lastname: Maiolica
authors.affiliation: Department of Pharmaceutical Sciences, University of Piemonte Orientale, via Bovio 2, 28100 Novara, Italy.
authors.forename: Francesca
authors.initials: F
authors.lastname: Rocchio
authors.affiliation: Department of Pharmaceutical Sciences, University of Piemonte Orientale, via Bovio 2, 28100 Novara, Italy.
authors.forename: Maria Giulia
authors.initials: MG
authors.lastname: Prato
authors.affiliation: Department of Biology, Institute of Molecular Systems Biology, Eidgenössische Technische Hochschule Zurich (ETHZ), 8093 Zurich, Switzerland; Faculty of Science, University of Zurich, 8057 Zurich, Switzerland.
authors.forename: Ruedi
authors.initials: R
authors.lastname: Aebersold
authors.affiliation: Department of Pharmaceutical Sciences, University of Piemonte Orientale, via Bovio 2, 28100 Novara, Italy; Institute of Pharmacology and Toxicology, University of Zurich-Vetsuisse, 8057 Zurich, Switzerland. Electronic address: lorenza.penengo@uzh.ch.
authors.forename: Lorenza
authors.initials: L
authors.lastname: Penengo
mesh_terms: D000595:Amino Acid Sequence; D019313:BRCA1 Protein / Q000378:metabolism; D045744:Cell Line, Tumor; D002843:Chromatin / Q000378:metabolism; D004249:DNA Damage; D004260:DNA Repair; D057809:HEK293 Cells; D006657:Histones / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D008969:Molecular Sequence Data; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism; D000071857:Tumor Suppressor p53-Binding Protein 1; D025801:Ubiquitin / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D044763:Ubiquitin-Conjugating Enzymes / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D054875:Ubiquitination
chemical_list: D019313:BRCA1 Protein; D002843:Chromatin; C468783:H2AX protein, human; D006657:Histones; D047908:Intracellular Signaling Peptides and Proteins; D034741:RNA, Small Interfering; C498301:TP53BP1 protein, human; D000071857:Tumor Suppressor p53-Binding Protein 1; D025801:Ubiquitin; C097310:UBE2D3 protein, human; D044763:Ubiquitin-Conjugating Enzymes; C535210:RNF168 protein, human; D044767:Ubiquitin-Protein Ligases