Harmful DNA:RNA hybrids are formed in cis and in a Rad51-independent manner

Abstract

DNA:RNA hybrids constitute a well-known source of recombinogenic DNA damage. The current literature is in agreement with DNA:RNA hybrids being produced co-transcriptionally by the invasion of the nascent RNA molecule produced in cis with its DNA template. However, it has also been suggested that recombinogenic DNA:RNA hybrids could be facilitated by the invasion of RNA molecules produced in trans in a Rad51-mediated reaction. Here, we tested the possibility that such DNA:RNA hybrids produced in trans constitute a source of recombinogenic DNA damage taking advantage of Rad51-independent single-strand annealing recombination assays and new constructs designed to induce expression of mRNA transcripts in trans in the yeast Saccharomyces cerevisiae. We show that unscheduled and recombinogenic DNA:RNA hybrids are formed in cis during transcription and in a Rad51-independent manner.