title: Bridge-induced chromosome translocation in yeast relies upon a Rad54/Rdh54-dependent, Pol32-independent pathway.
abstract: While in mammalian cells the genetic determinism of chromosomal translocation remains unclear, the yeast Saccharomyces cerevisiae has become an ideal model system to generate ad hoc translocations and analyze their cellular and molecular outcome. A linear DNA cassette carrying a selectable marker flanked by perfect homologies to two chromosomes triggers a bridge-induced translocation (BIT) in budding yeast, with variable efficiency. A postulated two-step process to produce BIT translocants is based on the cooperation between the Homologous Recombination System (HRS) and Break-Induced Replication (BIR); however, a clear indication of the molecular factors underlying the genetic mechanism is still missing. In this work we provide evidence that BIT translocation is elicited by the Rad54 helicase and completed by a Pol32-independent replication pathway. Our results demonstrate also that Rdh54 is involved in the stability of the translocants, suggesting a mitotic role in chromosome pairing and segregation. Moreover, when RAD54 is over-expressed, an ensemble of secondary rearrangements between repeated DNA tracts arise after the initial translocation event, leading to severe aneuploidy with loss of genetic material, which prompts the identification of fragile sites within the yeast genome.
authors.affiliation: Yeast Molecular Genetics Laboratory, International Centre for Genetic Engineering and Biotechnology, Trieste, Italy. tosato@icgeb.org
authors.forename: Valentina
authors.initials: V
authors.lastname: Tosato
authors.forename: Sabrina
authors.initials: S
authors.lastname: Sidari
authors.forename: Carlo V
authors.initials: CV
authors.lastname: Bruschi
mesh_terms: D001483:Base Sequence; D015139:Blotting, Southern; D015825:Chromosomes, Fungal; D053903:DNA Breaks, Double-Stranded; D004265:DNA Helicases / Q000378:metabolism; D045643:DNA Repair Enzymes / Q000378:metabolism; D004261:DNA Replication; D026942:DNA Topoisomerases / Q000378:metabolism; D004259:DNA-Directed DNA Polymerase / Q000378:metabolism; D005816:Genetic Complementation Test; D008957:Models, Genetic; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D011995:Recombination, Genetic / Q000235:genetics; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D014178:Translocation, Genetic / Q000235:genetics*
chemical_list: C522758:Pol32 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D004259:DNA-Directed DNA Polymerase; C075468:RAD54 protein, S cerevisiae; D004265:DNA Helicases; D026942:DNA Topoisomerases; C541336:RDH54 protein, S cerevisiae; D045643:DNA Repair Enzymes