Elevated dNTP levels suppress hyper-recombination in Saccharomyces cerevisiae S-phase checkpoint mutants.
MEC1, the essential yeast homolog of the human ATR/ATM genes, controls the S-phase checkpoint and prevents replication fork collapse at slow zones of DNA replication. The viability of hypomorphic mec1-21 is reduced in the rad52 mutant, defective in homologous recombination, suggesting that replication generates recombinogenic lesions. We previously observed a 6-, 10- and 30-fold higher rate of spontaneous sister chromatid exchange (SCE), heteroallelic recombination and translocations, respectively, in mec1-21 mutants compared to wild-type. Here we report that the hyper-recombination phenotype correlates with lower deoxyribonucleoside triphosphate (dNTP) levels, compared to wild-type. By introducing a dun1 mutation, thus eliminating inducible expression of ribonucleotide reductase in mec1-21, rates of spontaneous SCE increased 15-fold above wild-type. All the hyper-recombination phenotypes were reduced by SML1 deletions, which increase dNTP levels. Measurements of dNTP pools indicated that, compared to wild-type, there was a significant decrease in dNTP levels in mec1-21, dun1 and mec1-21 dun1, while the dNTP levels of mec1-21 sml1, mec1-21 dun1 sml1 and sml1 mutants were approximately 2-fold higher. Interestingly, higher dNTP levels in mec1-21 dun1 sml1 correlate with approximately 2-fold higher rate of spontaneous mutagenesis, compared to mec1-21 dun1. We suggest that higher dNTP levels in specific checkpoint mutants suppress the formation of recombinogenic lesions.
Fasullo
Michael
M
Ordway Research Institute, 150 New Scotland Avenue, Albany, NY 12209, USA. mfasullo@ordwayresearch.org
Tsaponina
Olga
O
Sun
Mingzeng
M
Chabes
Andrei
A
D018797:Cell Cycle Proteins / Q000235:genetics; D003854:Deoxyribonucleotides / Q000378:metabolism*; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics*; D016296:Mutagenesis; D009154:Mutation; D017346:Protein Serine-Threonine Kinases / Q000235:genetics*; D011995:Recombination, Genetic; D016196:S Phase / Q000235:genetics; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000235:genetics* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics*; D012854:Sister Chromatid Exchange; D000071164:Trefoil Factor-2
D018797:Cell Cycle Proteins; D003854:Deoxyribonucleotides; D047908:Intracellular Signaling Peptides and Proteins; C115052:SML1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; C000604007:TFF2 protein, human; D000071164:Trefoil Factor-2; C104169:DUN1 protein, S cerevisiae; C088937:MEC1 protein, S cerevisiae; D017346:Protein Serine-Threonine Kinases