RNA∶DNA hybrids initiate quasi-palindrome-associated mutations in highly transcribed yeast DNA.
RNase H enzymes promote genetic stability by degrading aberrant RNA:DNA hybrids and by removing ribonucleotide monophosphates (rNMPs) that are present in duplex DNA. Here, we report that loss of RNase H2 in yeast is associated with mutations that extend identity between the arms of imperfect inverted repeats (quasi-palindromes or QPs), a mutation type generally attributed to a template switch during DNA synthesis. QP events were detected using frameshift-reversion assays and were only observed under conditions of high transcription. In striking contrast to transcription-associated short deletions that also are detected by these assays, QP events do not require Top1 activity. QP mutation rates are strongly affected by the direction of DNA replication and, in contrast to their elevation in the absence of RNase H2, are reduced when RNase H1 is additionally eliminated. Finally, transcription-associated QP events are limited by components of the nucleotide excision repair pathway and are promoted by translesion synthesis DNA polymerases. We suggest that QP mutations reflect either a transcription-associated perturbation of Okazaki-fragment processing, or the use of a nascent transcript to resume replication following a transcription-replication conflict.
Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina, United States of America.
Nayun
N
Kim
Jang-Eun
JE
Cho
Yue C
YC
Li
Sue
S
Jinks-Robertson
D004247:DNA / Q000096:biosynthesis* / Q000235:genetics; D004260:DNA Repair / Q000235:genetics; D004259:DNA-Directed DNA Polymerase / Q000235:genetics; D016368:Frameshift Mutation; D055029:Inverted Repeat Sequences / Q000235:genetics*; D012313:RNA / Q000235:genetics; D016914:Ribonuclease H / Q000235:genetics*; D012265:Ribonucleotides / Q000235:genetics; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000235:genetics
C022262:Okazaki fragments; D012265:Ribonucleotides; D012313:RNA; D004247:DNA; D004259:DNA-Directed DNA Polymerase; C091139:ribonuclease HII; D016914:Ribonuclease H; C078856:ribonuclease HI