Deinococcus radiodurans HD-Pnk, a Nucleic Acid End-Healing Enzyme, Abets Resistance to Killing by Ionizing Radiation and Mitomycin C

End healing is a process whereby nucleic acid breaks with “dirty” 3′-PO4 or 2′,3′-cyclic-PO4 and 5′-OH ends are converted to 3′-OH and 5′-PO4 termini that are amenable to downstream repair reactions.Deinococcus radiodurans is resistant to massive doses of ionizing radiation (IR) that generate hundreds of dirty DNA double-strand breaks and thousands of single-strand breaks. This study highlightsDeinococcus HD-Pnk as a bifunctional 3′- and 5′-end-healing enzyme that helps protect against killing by IR. HD-Pnk appears to act late in the process of post-IR recovery, subsequent to genome reassembly from shattered fragments. HD-Pnk also contributes to resistance to killing by mitomycin C. These findings are significant in that they establish a role for end-healing enzymes in bacterial DNA damage repair.