Defective break-induced replication leads to half-crossovers in Saccharomyces cerevisiae.
Break-induced replication (BIR) is an important process of DNA metabolism that has been implicated in the restart of collapsed replication forks, as well as in various chromosomal instabilities, including loss of heterozygosity, translocations, and alternative telomere lengthening. Therefore, knowledge of how BIR is carried out and regulated is important for better understanding the maintenance of genomic stability in eukaryotes. Here we present a new yeast experimental system that enables the genetic control of BIR to be investigated. Analysis of mutations selected on the basis of their sensitivity to various DNA-damaging agents demonstrated that deletion of POL32, which encodes a third, nonessential subunit of polymerase delta, significantly reduced the efficiency of BIR, although some POL32-independent BIR was still observed. Importantly, the BIR defect in pol32Delta cells was associated with the formation of half-crossovers. We propose that these half-crossovers resulted from aberrant processing of BIR intermediates. Furthermore, we suggest that the half-crossovers observed in our system are analogous to nonreciprocal translocations (NRTs) described in mammalian tumor cells and, thus, our system could represent an opportunity to further study the NRT mechanism in yeast.
Deem
Angela
A
Department of Biology, School of Science, Indiana University-Purdue University Indianapolis, Indianapolis, Indiana 46202-5132, USA.
Barker
Krista
K
Vanhulle
Kelly
K
Downing
Brandon
B
Vayl
Alexandra
A
Malkova
Anna
A
D053903:DNA Breaks, Double-Stranded; D004261:DNA Replication; D004259:DNA-Directed DNA Polymerase / Q000235:genetics / Q000378:metabolism; D008957:Models, Genetic; D009154:Mutation; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism
C522758:Pol32 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D004259:DNA-Directed DNA Polymerase