Originally published as Genetics Published Articles Ahead of Print on August 9, 2008.

Genetics, Vol. 179, 1845-1860, August 2008, Copyright © 2008
doi:10.1534/genetics.108.087940

Defective Break-Induced Replication Leads to Half-Crossovers in Saccharomyces cerevisiae

Angela Deem, Krista Barker, Kelly VanHulle, Brandon Downing, Alexandra Vayl and Anna Malkova1

Department of Biology, School of Science, Indiana University–Purdue University Indianapolis, Indianapolis, Indiana 46202-5132

1 Corresponding author: Biology Department, Indiana University–Purdue University Indianapolis, 723 W. Michigan St., Indianapolis, IN, 46202-5132
E-mail: amalkova{at}iupui.edu

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 pol32{Delta} 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.


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Genetics 2008 179: NP. [Full Text]