A Role for Small RNAs in DNA Double-Strand Break Repair

Here we identify a novel class of small RNAs that are ~21-nucleotide in length and are produced from the sequences in the vicinity of DNA double strand break (DSB) sites in Arabidopsis and humans. We named them diRNAs for DSB-induced small RNAs. In Arabidopsis, the biogenesis of diRNAs requires the PI3 kinase ATR, RNA polymerase IV (Pol IV), and Dicer-like proteins. Mutations in these proteins as well as in Pol V cause significant reduction in DSB repair efficiency. diRNAs are recruited by Argonaute 2 (AGO2) to mediate DSB repair. In humans, knocking down Dicer or Ago2 causes a significant reduction in DSB repair. Our findings reveal a novel biological function for small RNAs in the DSB repair pathway. We propose that diRNAs may function as guide molecules for chromatin modifications or recruitment of repair complexes at DSB sites to facilitate repair.