title: Ubc9- and mms21-mediated sumoylation counteracts recombinogenic events at damaged replication forks.
abstract: The Ubc9 SUMO-conjugating enzyme and the Siz1 SUMO ligase sumoylate several repair and recombination proteins, including PCNA. Sumoylated PCNA binds Srs2, a helicase counteracting certain recombination events. Here we show that ubc9 mutants depend on checkpoint, recombination, and replication genes for growth. ubc9 cells maintain stalled-fork stability but exhibit a Rad51-dependent accumulation of cruciform structures during replication of damaged templates. Mutations in the Mms21 SUMO ligase resemble the ubc9 mutations. However, siz1, srs2, or pcna mutants altered in sumoylation do not exhibit the ubc9/mms21 phenotype. Like ubc9/mms21 mutants, sgs1 and top3 mutants also accumulate X molecules at damaged forks, and Sgs1/BLM is sumoylated. We propose that Ubc9 and Mms21 act in concert with Sgs1 to resolve the X structures formed during replication. Our results indicate that Ubc9- and Mms21-mediated sumoylation functions as a regulatory mechanism, different from that of replication checkpoints, to prevent pathological accumulation of cruciform structures at damaged forks.
authors.affiliation: FIRC Institute of Molecular Oncology Foundation and Department of Biomedical Sciences and Biotechnology, Università degli Studi di Milano, Via Adamello 16, 20139 Milan, Italy. dana.branzei@ifom-ieo-campus.it
authors.forename: Dana
authors.initials: D
authors.lastname: Branzei
authors.forename: Julie
authors.initials: J
authors.lastname: Sollier
authors.forename: Giordano
authors.initials: G
authors.lastname: Liberi
authors.forename: Xiaolan
authors.initials: X
authors.lastname: Zhao
authors.forename: Daisuke
authors.initials: D
authors.lastname: Maeda
authors.forename: Masayuki
authors.initials: M
authors.lastname: Seki
authors.forename: Takemi
authors.initials: T
authors.lastname: Enomoto
authors.forename: Kunihiro
authors.initials: K
authors.lastname: Ohta
authors.forename: Marco
authors.initials: M
authors.lastname: Foiani
mesh_terms: D004249:DNA Damage; D004265:DNA Helicases / Q000235:genetics / Q000378:metabolism; D004261:DNA Replication; D004271:DNA, Fungal / Q000502:physiology*; D044127:Epigenesis, Genetic; D005800:Genes, Fungal; D009154:Mutation; D018809:Proliferating Cell Nuclear Antigen / Q000235:genetics / Q000378:metabolism; D053484:RecQ Helicases; D011995:Recombination, Genetic; D025842:SUMO-1 Protein / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D044763:Ubiquitin-Conjugating Enzymes / Q000235:genetics / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism
chemical_list: D004271:DNA, Fungal; C500948:Mms21 protein, S cerevisiae; D018809:Proliferating Cell Nuclear Antigen; D025842:SUMO-1 Protein; D029701:Saccharomyces cerevisiae Proteins; C502374:TOP3 protein, S cerevisiae; C061376:SRS2 protein, S cerevisiae; D044763:Ubiquitin-Conjugating Enzymes; D044767:Ubiquitin-Protein Ligases; C090472:SGS1 protein, S cerevisiae; D004265:DNA Helicases; D053484:RecQ Helicases; C436837:Siz1 protein, S cerevisiae