Chromosome integrity at a double-strand break requires exonuclease 1 and MRX.
The continuity of duplex DNA is generally considered a prerequisite for chromosome continuity. However, as previously shown in yeast as well as human cells, the introduction of a double-strand break (DSB) does not generate a chromosome break (CRB) in yeast or human cells. The transition from DSB to CRB was found to be under limited control by the tethering function of the RAD50/MRE11/XRS2 (MRX) complex. Using a system for differential fluorescent marking of both sides of an endonuclease-induced DSB in single cells, we found that nearly all DSBs are converted to CRBs in cells lacking both exonuclease 1 (EXO1) activity and MRX complex. Thus, it appears that some feature of exonuclease processing or resection at a DSB is critical for maintaining broken chromosome ends in close proximity. In addition, we discovered a thermal sensitive (cold) component to CRB formation in an MRX mutant that has implications for chromosome end mobility and/or end-processing.
National Institute of Environmental Health Sciences, NIH, Laboratory of Molecular Genetics, Research Triangle Park, NC 27709, USA.
Wataru
W
Nakai
Jim
J
Westmoreland
Elaine
E
Yeh
Kerry
K
Bloom
Michael A
MA
Resnick
D019457:Chromosome Breakage; D015825:Chromosomes, Fungal / Q000378:metabolism; D053903:DNA Breaks, Double-Stranded; D004265:DNA Helicases / Q000235:genetics / Q000378:metabolism*; D004706:Endodeoxyribonucleases / Q000235:genetics / Q000378:metabolism*; D005090:Exodeoxyribonucleases / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D017384:Sequence Deletion; D013696:Temperature
D029701:Saccharomyces cerevisiae Proteins; C086929:XRS2 protein, S cerevisiae; D004706:Endodeoxyribonucleases; D005090:Exodeoxyribonucleases; C094191:MRE11 protein, S cerevisiae; C028450:exodeoxyribonuclease I; C076225:RAD5 protein, S cerevisiae; D004265:DNA Helicases