The Bcl-2 family members are evolutionally conserved and crucial regulators of apoptosis. Diva (Boo), an ortholog of Bcl2L10 or Bcl-B, is a member of the Bcl-2 family that has contradictory functions in apoptosis. To understand the signaling mechanisms of Diva, we searched for proteins that interact with Diva using the yeast two-hybrid system. We identified a nucleoside diphosphate kinase isoform, NM23-H2. Here, we show that Diva bound to NM23-H2 in cells in which the transmembrane domain of Diva was required, and both proteins were colocalized in cytoplasm. Of interest, Diva protein level was significantly down-regulated by NM23-H2 as knock down of NM23-H2 restored Diva expression. Overexpression of NM23-H2 induced apoptosis, and the depletion of NM23-H2 led to the increase of Diva's apoptotic activity. Thus, these results indicate the existence of a previously undiscovered mechanism by which NM23-H2 involves in the regulation of Diva-mediated apoptosis. (C) 2007 Elsevier Inc. All rights reserved.