Abstract 842: ADAR and DDX54 promote genomic stability in breast cancer cells

Abstract

Adenosine deaminase acting on RNA (ADAR) is an RNA-editing enzyme that binds dsRNA and converts adenosine to inosine. ADAR promotes cell survival and proliferation in multiple types of tumors, including breast cancer. However, the mechanism of ADAR-driven oncogenicity is not fully established. We focused on ADAR p110, the constitutively expressed and nuclear-localized isoform, and its role in managing genotoxic stress in cancer. ADAR p110 is involved in resolving R-loops, the DNA-RNA hybrids produced during transcription, and DNA damage response (DDR). We sought to elucidate the mechanism of ADAR-associated R-loop resolution and DDR that can be targeted in breast cancer. To identify ADAR-interacting proteins, proximity labeling was performed using ADAR p110 fused to ascorbate peroxidase (APEX2), followed by mass spectrometry. Among the positively enriched hits, known ADAR-interacting proteins associated with R-loop and DDR were validated by immunoprecipitation and immunofluorescence. DEAD-box helicase DDX54 was among the nine RNA helicases interacting with ADAR. DDX54 and ADAR showed an additive effect on preventing γH2AX signal. Additionally, knockdown (KD) of DDX54 increased ADAR expression, whereas ADAR KD did not affect DDX54 expression. These results suggest that DDX54 coordinates with ADAR to prevent genotoxic stress in breast cancer cells. As DDX54 and ADAR are both associated with R-loop resolution and DDR, we hypothesize that DDX54 and ADAR suppress R-loop accumulation and/or other types of genotoxic stress. This may be through independent pathways despite the physical interaction between ADAR and DDX54. Citation Format: Sua Ryu, Kyle A. Cottrell, Luisángely Soto-Torres, Angela Schabb, Jason D. Weber. ADAR and DDX54 promote genomic stability in breast cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 842.