Poster Presentation 44th Lorne Genome Conference 2023

Revealing the real R-loop landscape in the S. pombe genome (#247)

Jing Zhang 1 , Attila Horvath 1 , Nicole Thomsen 1 , Tamas Fischer 1
  1. The John Curtin School of Medical Research, The Australian National University, Canberra, ACT, Australia

R-loops, a three-stranded nucleic acid structure consisting of an RNA-DNA hybrid and a single-stranded DNA, have been found to be widespread in eukaryotic genomes. While R-loops have been shown to function in many nuclear processes, including transcription regulation, replication and DNA repair, they have also been associated with genomic instability and DNA damage. Countless R-loop maps have been generated in various organisms, however, the overlap in results across various techniques and laboratories is surprisingly low. In addition, the majority of R-loop signals were not tested or were insensitive to RNaseH treatment, raising questions about the reliability of these datasets.   

Here we describe the development of a stringent method to detect R-loops in the S.pombe genome. Our method is highly specific with nearly 100% of identified R-loops being sensitive to RNaseH treatment. Interestingly, we can observe widespread R-loop signal in RNaseH-deficient strains, but do not detect the presence of R-loops in WT strains that contain RNaseH enzymes. Our results suggest that R-loops are extremely transient structures in S.pombe, due to their very quick degradation by cellular RNaseH enzymes, and published R-loop maps in WT cells likely represent mainly non-specific background signal. We expect that our findings will also be applicable to other organisms.  

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