Proofreading of ribonucleotides inserted into DNA by yeast DNA polymerase ε

• Published in: DNA repair Vol. 11; no. 8; pp. 649 - 656
• Main Authors: WILLIAMS, Jessica S, CLAUSES, Anders R, NICK MCELHINNY, Stephanie A, WATTS, Brian E, JOHANSSON, Erik, KUNKEL, Thomas A
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier 01.08.2012
• Subjects: Bacteriology; Biological and medical sciences; Fundamental and applied biological sciences. Psychology; Growth, nutrition, cell differenciation; Microbiology; Molecular and cellular biology; Molecular genetics; Mutagenesis. Repair; Replication; DNA replication; Yeast; Enzyme; Transferases; DNA polymerase ε; Nucleotidyltransferases; Exonuclease; Ribonucleotides; Proofreading; DNA; Replication; Repair; DNA-directed DNA polymerase
• ISSN: 1568-7864; 1568-7856
• DOI: 10.1016/j.dnarep.2012.05.004

We have investigated the ability of the 3′ exonuclease activity of S. cerevisiae DNA polymerase ε (Pol ε) to proofread newly inserted ribonucleotides (rNMPs). During DNA synthesis in vitro , Pol ε proofreads ribonucleotides with apparent efficiencies that vary from none at some locations to more than 90% at others, with rA and rU being more efficiently proofread than rC and rG. Previous studies show that failure to repair ribonucleotides in the genome of rnh201 Δ strains that lack RNase H2 activity elevates the rate of short deletions in tandem repeat sequences. Here we show that this rate is increased by 2–4-fold in pol2–4 rnh201 Δ strains that are also defective in Pol ε proofreading. In comparison, defective proofreading in these same strains increases the rate of base substitutions by more than 100-fold. Collectively, the results indicate that although proofreading of an ‘incorrect’ sugar is less efficient than is proofreading of an incorrect base, Pol ε does proofread newly inserted rNMPs to enhance genome stability.