title: Condensin loaded onto the replication fork barrier site in the rRNA gene repeats during S phase in a FOB1-dependent fashion to prevent contraction of a long repetitive array in Saccharomyces cerevisiae.
abstract: An average of 200 copies of the rRNA gene (rDNA) is clustered in a long tandem array in Saccharomyces cerevisiae. FOB1 is known to be required for expansion/contraction of the repeats by stimulating recombination, thereby contributing to the maintenance of the average copy number. In Deltafob1 cells, the repeats are still maintained without any fluctuation in the copy number, suggesting that another, unknown system acts to prevent repeat contraction. Here, we show that condensin acts together with FOB1 in a functionally complemented fashion to maintain the long tandem repeats. Six condensin mutants possessing severely contracted rDNA repeats were isolated in Deltafob1 cells but not in FOB1+ cells. We also found that the condensin complex associated with the nontranscribed spacer region of rDNA with a major peak coincided with the replication fork barrier (RFB) site in a FOB1-dependent fashion. Surprisingly, condensin association with the RFB site was established during S phase and was maintained until anaphase. These results indicate that FOB1 plays a novel role in preventing repeat contraction by regulating condensin association and suggest a link between replication termination and chromosome condensation and segregation.
authors.affiliation: Laboratory of Genome Dynamics, National Institute for Basic Biology, 38 Nishigonaka, Myodaiji, Okazaki 444-8585, Japan.
authors.forename: Katsuki
authors.initials: K
authors.lastname: Johzuka
authors.forename: Masahiro
authors.initials: M
authors.lastname: Terasawa
authors.forename: Hideyuki
authors.initials: H
authors.lastname: Ogawa
authors.forename: Tomoko
authors.initials: T
authors.lastname: Ogawa
authors.forename: Takashi
authors.initials: T
authors.lastname: Horiuchi
mesh_terms: D000251:Adenosine Triphosphatases / Q000235:genetics* / Q000378:metabolism; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D018797:Cell Cycle Proteins; D049109:Cell Proliferation; D020090:Chromosome Segregation; D004261:DNA Replication; D004275:DNA, Ribosomal / Q000235:genetics / Q000378:metabolism; D021903:DNA, Ribosomal Spacer; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism*; D005804:Genes, Lethal; D046912:Multiprotein Complexes / Q000235:genetics* / Q000378:metabolism; D009154:Mutation; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D021122:Protein Subunits; D012335:RNA, Ribosomal / Q000235:genetics* / Q000378:metabolism; D012091:Repetitive Sequences, Nucleic Acid; D016196:S Phase / Q000235:genetics; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D004275:DNA, Ribosomal; D021903:DNA, Ribosomal Spacer; D004268:DNA-Binding Proteins; C105579:FOB1 protein, S cerevisiae; D046912:Multiprotein Complexes; D009687:Nuclear Proteins; D021122:Protein Subunits; D012335:RNA, Ribosomal; C090455:SMC2 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; C108312:condensin complexes; D000251:Adenosine Triphosphatases