title: Complementary functions of the Saccharomyces cerevisiae Rad2 family nucleases in Okazaki fragment maturation, mutation avoidance, and chromosome stability.
abstract: Rad2 family nucleases, identified by sequence similarity within their catalytic domains, function in multiple pathways of DNA metabolism. Three members of the Saccharomyces cerevisiae Rad2 family, Rad2, Rad27, and exonuclease 1 (Exo1), exhibit both 5' exonuclease and flap endonuclease activities. Deletion of RAD27 results in defective Okazaki fragment maturation, DNA repair, and subsequent defects in mutation avoidance and chromosomal stability. However, strains lacking Rad27 are viable. The expression profile of EXO1 during the cell cycle is similar to that of RAD27 and other genes encoding proteins that function in DNA replication and repair, suggesting Exo1 may function as a back up nuclease for Rad27 in DNA replication. We show that overexpression of EXO1 suppresses multiple rad27 null mutation-associated phenotypes derived from DNA replication defects, including temperature sensitivity, Okazaki fragment accumulation, the rate of minichromosome loss, and an elevated mutation frequency. While generally similar findings were observed with RAD2, overexpression of RAD2, but not EXO1, suppressed the MMS sensitivity of the rad27 null mutant cells. This suggests that Rad2 can uniquely complement Rad27 in base excision repair (BER). Furthermore, Rad2 and Exo1 complemented the mutator phenotypes and cell cycle defects of rad27 mutant strains to differing extents, suggesting distinct in vivo nucleic acid substrates.
authors.affiliation: Division of Molecular Biology, City of Hope National Medical Center, Duarte, CA 91010, USA.
authors.forename: Xuemin
authors.initials: X
authors.lastname: Sun
authors.forename: Douglas
authors.initials: D
authors.lastname: Thrower
authors.forename: Junzhuan
authors.initials: J
authors.lastname: Qiu
authors.forename: Phillis
authors.initials: P
authors.lastname: Wu
authors.forename: Li
authors.initials: L
authors.lastname: Zheng
authors.forename: Mian
authors.initials: M
authors.lastname: Zhou
authors.forename: Jeff
authors.initials: J
authors.lastname: Bachant
authors.forename: David M
authors.initials: DM
authors.lastname: Wilson
authors.forename: Binghui
authors.initials: B
authors.lastname: Shen
mesh_terms: D002453:Cell Cycle / Q000235:genetics; D043171:Chromosomal Instability / Q000235:genetics*; D004247:DNA / Q000235:genetics*; D017931:DNA Primers; D004268:DNA-Binding Proteins / Q000235:genetics; D004706:Endodeoxyribonucleases / Q000235:genetics; D005090:Exodeoxyribonucleases / Q000235:genetics*; D045585:Flap Endonucleases / Q000235:genetics; D015870:Gene Expression; D015151:Immunoblotting; D008856:Microscopy, Fluorescence; D009154:Mutation / Q000235:genetics; D010957:Plasmids; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics; D013696:Temperature
chemical_list: D017931:DNA Primers; D004268:DNA-Binding Proteins; C022262:Okazaki fragments; D029701:Saccharomyces cerevisiae Proteins; C073998:RAD2 protein, S cerevisiae; D004247:DNA; D004706:Endodeoxyribonucleases; D005090:Exodeoxyribonucleases; D045585:Flap Endonucleases; C028450:exodeoxyribonuclease I; C468323:RAD27 protein, S cerevisiae