Normal processing of AP sites in Apn1-deficient Saccharomyces cerevisiae is restored by Escherichia coli genes expressing either exonuclease III or endonuclease III

Jean Yves Masson, Dindial Ramotar*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

27 Citations (Scopus)

Abstract

Escherichia coil exonuclease III and endonuclease III are two distinct DNA-repair enzymes that can cleave apurinic/apyrimidinic (AP) sites by different mechanisms. While the AP endonuclease activity of exonuclease III generates a 3'-hydroxyl group at AP sites, the AP lyase activity of endonuclease III produces a 3'-α,β unsaturated aldehyde that prevents DNA-repair synthesis. Saccharomyces cerevisiae Apn1 is the major AP endonuclease/3'-diesterase that also produces a 3'-hydroxyl group at the AP site, but it is unrelated to either exonuclease III or endonuclease III. apn1 deletion mutants are unable to repair AP sites generated by the alkylating agent methyl methane sulphonate and display a spontaneous mutator phenotype. This work shows that either exonuclease III or endonuclease HI can functionally replace yeast Apn1 in the repair of AP sites. Two conclusions can be derived from these findings. The first of these conclusions is that yeast cells can complete the repair of AP sites even though they are cleaved by AP lyase. This implies that AP lyase can contribute significantly to the repair of AP sites and that yeast cells have the ability to process the α,β unsaturated aldehyde produced by endonuclease III. The second of these conclusions is that unrepaired AP sites are strictly the cause of the high spontaneous mutation rate in the apn1 deletion mutant.

Original languageEnglish
Pages (from-to)711-721
Number of pages11
JournalMolecular Microbiology
Volume24
Issue number4
DOIs
Publication statusPublished - 1997
Externally publishedYes

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