Identification of APN2, the Saccharomyces cerevisiae homolog of the major human AP endonuclease HAP1, and its role in the repair of abasic sites

Article Abstract:

APN2 is the Saccharomyces cerevisiae homolog of the major human abasic (AP) endonuclease HAP1. Its role in repair of AP sites has been explored. These sites arise in DNA through spontaneous base loss. Damaged bases are removed by enzymes. APN1 (ital) encodes the major AP-endonuclease of the yeast. Human HAP1 (REF1) (ital) encodes the major AP endonuclease which acts as a redox regulatory protein. It also acts in DNA repair. There is evidence that Apn1 and Apn2 are alternate pathways for AP site repair. AP sites seem to be very cytotoxic and mutagenic in eukaryotes. The mutagenic bypass of AP sites seem to be mediated by the REV3, REV7-encoded DNA polymerase zeta.

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Roles of yeast DNA polymerases delta and zeta and of Rev1 in the bypass of abasic sites

Article Abstract:

Efficient bypass of an abasic (AP) site by the combined action of yeast DNA polymerases delta and zeta has been shown. From the pattern of mutations brought on by AP sites in yeast, it appears likely that in vivo A nucleotide is the residue inserted most often opposite AP sites. Biochemical studies make it appear that Pol delta usually inserts an A opposite the AP site. Efficient bypass of the lesion occurs when Pol delta and Pol zeta are together. Steady-state kinetic analyses show Pol zeta to be very inefficient in putting nucleotides opposite the PA site.

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Requirement of yeast Rad1-Rad10 nuclease for the removal of 3'-blocked termini from DNA strand breaks induced by reactive oxygen species

Article Abstract:

Genetic and biochemical evidence for the requirement of Rad1-Rad10 nuclease in the removal of 3'-blocked termini from DNA strand breaks induced on treatment of yeast cells with the oxidative DNA damaging agent H2O2 is presented. The genetics study indicates that 3'-blocked termini are removed in yeast by the three competing pathways that involve the Apn1, Apn2, and Rad1-Rad10 nucleases. It is shown that the Rad1-Rad10 nuclease efficiently cleaves DNA modifies with a 3'-phosphoglycolate terminus.

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