title: Branch migrating sister chromatid junctions form at replication origins through Rad51/Rad52-independent mechanisms.
abstract: Cells overcome intra-S DNA damage and replication impediments by coupling chromosome replication to sister chromatid-mediated recombination and replication-bypass processes. Further, molecular junctions between replicated molecules have been suggested to assist sister chromatid cohesion until anaphase. Using two-dimensional gel electrophoresis, we have identified, in yeast cells, replication-dependent X-shaped molecules that appear during origin activation, branch migrate, and distribute along the replicon through a mechanism influenced by the rate of fork progression. Their formation is independent of Rad51- and Rad52-mediated homologous recombination events and is not affected by DNA damage or replication blocks. Further, in hydroxyurea-treated rad53 mutants, altered in the replication checkpoint, the branched molecules progressively degenerate and likely contribute to generate pathological structures. We suggest that cells couple sister chromatid tethering with replication initiation by generating specialized joint molecules resembling hemicatenanes: this process might prime cohesion and assist sister chromatid-mediated recombination and replication events.
authors.affiliation: Istituto F.I.R.C. di Oncologia Molecolare, Via Adamello 16, Milano 20141, Italy.
authors.forename: Massimo
authors.initials: M
authors.lastname: Lopes
authors.forename: Cecilia
authors.initials: C
authors.lastname: Cotta-Ramusino
authors.forename: Giordano
authors.initials: G
authors.lastname: Liberi
authors.forename: Marco
authors.initials: M
authors.lastname: Foiani
mesh_terms: D018797:Cell Cycle Proteins; D064447:Checkpoint Kinase 2; D002842:Chromatids / Q000378:metabolism*; D004249:DNA Damage; D004254:DNA Nucleotidyltransferases / Q000378:metabolism*; D004261:DNA Replication; D004271:DNA, Fungal / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D009690:Nucleic Acid Conformation; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism; D051135:Rad51 Recombinase; D051721:Rad52 DNA Repair and Recombination Protein; D011995:Recombination, Genetic; D018741:Replication Origin; D012093:Replicon; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism
chemical_list: D018797:Cell Cycle Proteins; D004271:DNA, Fungal; D004268:DNA-Binding Proteins; C497197:RAD52 protein, S cerevisiae; D051721:Rad52 DNA Repair and Recombination Protein; D029701:Saccharomyces cerevisiae Proteins; D064447:Checkpoint Kinase 2; D017346:Protein Serine-Threonine Kinases; C067022:RAD53 protein, S cerevisiae; D004254:DNA Nucleotidyltransferases; C495151:RAD51 protein, S cerevisiae; D051135:Rad51 Recombinase