Abstract 1124: Site-specific DICER and DROSHA RNA products control the DNA-damage response.

Abstract The DNA damage response (DDR) is a signaling pathway that arrests the proliferation of cells undergoing genotoxic events to preserve genome stability and as such plays important tumor suppressing functions. DICER and DROSHA are crucial ribonucleases involved in RNA interference (RNAi). Components of RNAi are thought to have evolved to preserve genome stability from the attacks of viruses and mobile genetic elements. RNA products generated by DICER and DROSHA are involved in chromatin assembly, gene silencing and cancer. So far, RNAi and DDR pathways have not been demonstrated to directly interact. We have recently shown in human, mouse and zebrafish that DICER and DROSHA, but not downstream elements of the RNAi pathway, are necessary to activate the DDR upon exogenous DNA damage and oncogene-induced genotoxic stress, as studied by DDR foci formation and by checkpoint assays. Indeed, oncogene-induced senescent cells, upon DICER or DROSHA inactivation, escape DDR-imposed arrest and proliferate again. DDR foci are sensitive to RNase A treatment and DICER- and DROSHA-dependent RNA products are required to restore DDR foci in RNase-A-treated cells. Through RNA deep sequencing and the study of DDR activation at a single inducible DNA double-strand break, we demonstrate that DDR foci formation requires site-specific DICER- and DROSHA-dependent small RNAs, named DDRNAs, which act in a MRE11-RAD50-NBS1- complex-dependent manner to fuel DDR. DDRNAs, either chemically synthesized or in vitro generated by DICER cleavage, are sufficient to restore the DDR in RNase-A-treated cells, also in the absence of other cellular RNAs. We propose an unanticipated direct role of a novel class of ncRNAs in the control of DDR activation at sites of DNA damage. The relevance of these findings in the context of tumor suppression will be discussed. Citation Format: Fabrizio d'Adda di Fagagna. Site-specific DICER and DROSHA RNA products control the DNA-damage response. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1124. doi:10.1158/1538-7445.AM2013-1124