Effect of sequence context and direction of replication on AP site bypass in Saccharomyces cerevisiae

• Type of Material: Article
• Authors: Gaobin Bao, Emory University; Yoke Wah Kow, Emory University
• Language: English
• Date: 2009-10-02
• Publisher: Elsevier
• Publication Version: Author Accepted Manuscript (After Peer Review)
• Copyright Statement: © 2009 Elsevier B.V. All rights reserved.
• License: Creative Commons Attribution-NonCommerical-NoDerivs 3.0 Unported
• Final Published Version (URL): http://dx.doi.org/10.1016/j.mrfmmm.2009.06.006
• Title of Journal or Parent Work: Mutation Research - Fundamental and Molecular Mechanisms of Mutagenesis
• ISSN: 0027-5107
• Volume: 669
• Issue: 1-2
• Start Page: 147
• End Page: 154
• Grant/Funding Information: This work was supported by NIH grants CA90860 (Y.W.K.).
• Keywords: Sequence context; AP site bypass; Single strand oligonucleotide transformation; Direction of replication
• Research Categories: Biology, Genetics; Health Sciences, Oncology

Abstract

Yeast can be readily transformed by single-stranded oligonucleotides (ssOligos). Previously, we showed that an ssOligo that generates a 1-nt loop containing an AP site corrected the −1 frameshift mutation in the lys2ΔA746 allele. However, these experiments had to be performed in yeast apn1 mutants lacking the major AP endonuclease. In this study, we show that bypass of an AP site can be studied in repair-proficient yeast by using ssOligos that generates a 7-nt loop containing an AP site. The bypass studies performed using the ssOligos that generate a 7-nt loop was validated by demonstrating that the result obtained are similar to those derived using ssOligos containing a 1-nt loop in an apn1 mutant. By using the 7-nt loop system, we showed that the bypass efficiencies of AP sites are dependent on the sequence context that surrounds the lesion and are apparently no affected by the direction of DNA replication. In contrast, the mutagenic specificity of an AP site is not affected by the sequence context or the direction of replication. In all cases, dC is inserted at twice the frequency of dA opposite an AP site, indicating that REV1 is mainly responsible for bypass of AP sites at all lesion sites studied.