Involvement of an X family DNA polymerase in double‐stranded break repair in the radioresistant organism Deinococcus radiodurans

Summary DNA polymerases of the X family have been implicated in a variety of DNA repair processes in eukaryotes. Here we show that Deinococcus radiodurans , a highly radioresistant bacterium able to mend hundreds of radiation‐induced double‐stranded DNA breaks, expresses a DNA polymerase belonging to the X family. This novel bacterial polymerase, named PolX Dr , was identified as the product of the Deinococcal DR0467 gene. The purified PolX Dr protein possesses a DNA polymerase activity that is stimulated by MnCl 2 , a property of the X family DNA polymerases. Antibodies raised against PolX Dr recognized human pol λ, rat pol β and yeast Pol4 and, conversely, antibodies raised against these proteins recognized PolX Dr . This immunological cross‐reactivity suggests a high degree of structural conservation among the polymerases of the X family. Lack of PolX Dr reduced the rate of repair of double‐stranded DNA breaks and increased cell sensitivity to γ‐rays. PolX Dr thus appears to play an important role in double‐stranded DNA break repair in D. radiodurans.