Non-coding RNAs: an emerging player in DNA damage response.

Non-coding RNAs play a crucial role in maintaining genomic stability which is essential for cell survival and preventing tumorigenesis. Through an extensive crosstalk between non-coding RNAs and the canonical DNA damage response (DDR) signaling pathway, DDR-induced expression of non-coding RNAs can provide a regulatory mechanism to accurately control the expression of DNA damage responsive genes in a spatio-temporal manner. Mechanistically, DNA damage alters expression of a variety of non-coding RNAs at multiple levels including transcriptional regulation, post-transcriptional regulation, and RNA degradation. In parallel, non-coding RNAs can directly regulate cellular processes involved in DDR by altering expression of their targeting genes, with a particular emphasis on miRNAs and lncRNAs. MiRNAs are required for almost every aspect of cellular responses to DNA damage, including sensing DNA damage, transducing damage signals, repairing damaged DNA, activating cell cycle checkpoints, and inducing apoptosis. As for lncRNAs, they control transcription of DDR relevant gene by four different regulatory models, including signal, decoy, guide, and scaffold. In addition, we also highlight potential clinical applications of non-coding RNAs as biomarkers and therapeutic targets for anti-cancer treatments using DNA-damaging agents including radiation and chemotherapy. Although tremendous advances have been made to elucidate the role of non-coding RANs in genome maintenance, many key questions remain to be answered including mechanistically how non-coding RNA pathway and DNA damage response pathway is coordinated in response to genotoxic stress.