Human immunodeficiency virus type 1 Vpr protein binds to the uracil DNA glycosylase DNA repair enzyme

The role of the accessory gene product Vpr during human immunodeficie ncy virus type 1 infection remains unclear. We have used the yeast tw o-hybrid to identify cellular proteins that interact with Vpr and cou ld be involved in its function. A cDNA clone which encodes the human uracil DNA glycosylase (UNG), a DNA repair enzyme involved in removal of uracil in DNA, has been isolated. Interaction between Vpr and UNG has been demonstrated by in vitro protein-protein binding assays usi ng translated, radiolabeled Vpr and UNG recombinant proteins expresse d as a glutathione S-transferase fusion protein. Conversely, purified UNG has been demonstrated to interact with Vpr recombinant protein e xpressed as a glutathione S-transferase fusion protein. Coimmunopreci pitation experiments confirmed that Vpr and UNG are associated within cells expressing Vpr. By using a panel of C- and N-terminally delete d Vpr mutants, we have determined that the core protein of Vpr, spann ing amino acids 15 to 77, is involved in the interaction with UNG. We also demonstrate by in vitro experiments that the enzymatic activity of UNG is retained upon interaction with Vpr.