A low activity DNA endonuclease yielding 3'-hydroxyl ends (Probable). Upon expression enhances RecA-independent DNA recombination 19-fold, concomitantly reducing viability by 98% and inducing DNA damage as measured by induction of the SOS repair response. A quadruple rpnA-rpnB-rpnC-rpnD deletion shows no change in basal RecA-independent recombination. Belongs to the Rpn/YhgA-like nuclease family.