Abstract 6214: FANCA promotes transcription-coupled homologous recombination by catalyzing R-loops formation

Abstract

Abstract R loops arise from hybridization of RNA transcripts with template DNA during transcription, which are not only cause DNA damage in certain contexts as cancer hallmarks but also be important regulators of cellular processes. Recent findings revealed that DNA double-strand breaks (DSBs) elicit RNA-DNA hybrid formation. The RNA moiety of the R-loop displays an extraordinary potential to regulate multiple steps of homologous recombination (HR) by substituting for the double-stranded DNA (dsDNA) substrate on which DSB repair processes naturally occur. Here, we use the Damage At RNA Transcription assay to reveal colocalization of FANCA with R-loops in a highly transcribed genomic locus upon DNA damage. We further demonstrate FANCA participates in forming R-loops in the initial DSBs repair stage and assists in removing R-loops later. Besides, we find that highly purified human FANCA anneals synthetic single-stranded RNA (ssRNA) and ssDNA species to R-loops and binds R-loop substrates with high affinity, preferring guanine-rich sequences in vitro. Importantly, we illustrate that FANCA promotes HR efficiency via catalyzation of DNA: RNA hybrids at DSBs sites. Finally, a series of RNA and R-loop substrates are found to stimulate ID2 monoubiquitination, with activity corresponding to remove transient R- loops in later HR stage. In summary, our results support a mechanism whereby FANCA promotes the formation of temporary R-loops by annealing ssRNA and ssDNA species at DSBs in transcribed regions, thereby stimulating HR. Citation Format: Fang Li. FANCA promotes transcription-coupled homologous recombination by catalyzing R-loops formation. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6214.