A Recently Discovered Essential Factor for DNA Homologous Recombination:RNA Polymerase III

End resection is a central step in DNA homologous recombination (HR) and the HR-mediated repair of DNA double-strand breaks (DSBs), which degrades 5’-end strands at DSBs by several kilo-bases and thus creates 3’-end single-strand DNA overhangs. A critical long-standing question is how the 3’-end strands are protected during end resection. Now, this question is answered. Liu et al. found that the protection of 3’-end strands is achieved by the formation of an RNA-DNA hybrid. RNA polymerase III is responsible for catalyzing the RNA strand in the hybrid. Thus, RNA polymerase III is an essential factor for HR, and the RNA-DNA hybrid is an essential HR intermediate.