Low levels of DNA polymerase alpha induce mitotic and meiotic instability in the ribosomal DNA gene cluster of Saccharomyces cerevisiae.
The ribosomal DNA (rDNA) genes of Saccharomyces cerevisiae are located in a tandem array of about 150 repeats. Using a diploid with markers flanking and within the rDNA array, we showed that low levels of DNA polymerase alpha elevate recombination between both homologues and sister chromatids, about five-fold in mitotic cells and 30-fold in meiotic cells. This stimulation is independent of Fob1p, a protein required for the programmed replication fork block (RFB) in the rDNA. We observed that the fob1 mutation alone significantly increased meiotic, but not mitotic, rDNA recombination, suggesting a meiosis-specific role for this protein. We found that meiotic cells with low polymerase alpha had decreased Sir2p binding and increased Spo11p-catalyzed double-strand DNA breaks in the rDNA. Furthermore, meiotic crossover interference in the rDNA is absent. These results suggest that the hyper-Rec phenotypes resulting from low levels of DNA polymerase alpha in mitosis and meiosis reflect two fundamentally different mechanisms: the increased mitotic recombination is likely due to increased double-strand DNA breaks (DSBs) resulting from Fob1p-independent stalled replication forks, whereas the hyper-Rec meiotic phenotype results from increased levels of Spo11-catalyzed DSBs in the rDNA.
Casper
Anne M
AM
Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina, United States of America. anne.casper@duke.edu
Mieczkowski
Piotr A
PA
Gawel
Malgorzata
M
Petes
Thomas D
TD
D043171:Chromosomal Instability; D004256:DNA Polymerase I / Q000235:genetics / Q000378:metabolism*; D004250:DNA Topoisomerases, Type II / Q000378:metabolism; D004271:DNA, Fungal / Q000235:genetics; D004275:DNA, Ribosomal / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000378:metabolism; D004706:Endodeoxyribonucleases; D006655:Histone Deacetylases / Q000378:metabolism; D008540:Meiosis; D008938:Mitosis; D005810:Multigene Family; D010641:Phenotype; D011995:Recombination, Genetic; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000201:enzymology / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D038281:Silent Information Regulator Proteins, Saccharomyces cerevisiae / Q000378:metabolism; D056565:Sirtuin 2; D037761:Sirtuins / Q000378:metabolism; D000099257:Meiotic Recombination Protein SPO11
D004256:DNA Polymerase I; D004250:DNA Topoisomerases, Type II; D004271:DNA, Fungal; D004275:DNA, Ribosomal; D004268:DNA-Binding Proteins; D004706:Endodeoxyribonucleases; D006655:Histone Deacetylases; D029701:Saccharomyces cerevisiae Proteins; D038281:Silent Information Regulator Proteins, Saccharomyces cerevisiae; D056565:Sirtuin 2; D037761:Sirtuins; C105579:FOB1 protein, S cerevisiae; C083536:POL1 protein, S cerevisiae; C518938:Spo11 protein, S cerevisiae; D000099257:Meiotic Recombination Protein SPO11; C087778:SIR2 protein, S cerevisiae