HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1 VPR INTERACTS WITH HHR23A, A CELLULAR PROTEIN IMPLICATED IN NUCLEOTIDE EXCISION DNA-REPAIR

The human immunodeficiency virus type 1 (HIV-1) vpr gene is an evoluti onarily conserved gene among the primate lentiviruses HIV-1, HIV-2, an d simian immunodeficiency viruses. One of the unique functions attribu ted to the vpr gene product is the arrest of cells in the G(2) phase o f the cell cycle. Here we demonstrate that Vpr interacts physically wi th HHR23A, one member of an evolutionarily conserved gene family invol ved in nucleotide excision repair. Interaction of Vpr with HHR23A was initially identified through a yeast two-hybrid screen and was confirm ed by the demonstration of direct binding between bacterially expresse d recombinant and transiently expressed or chemically synthesized prot ein products. Visualization of HHR23A and Vpr by indirect immunofluore scence and confocal microscopy indicates that the two proteins colocal ize at or about the nuclear membrane. We also map the Vpr-binding doma in in HHR23A to a C-terminal 45-amino-acid region of the protein previ ously shown to have homology to members of the ubiquitination pathway. Overexpression of HHR23A and a truncated derivative which includes th e Vpr-binding domain results in a partial alleviation of the G(2) arre st induced by Vpr, suggesting that the interaction between Vpr and HHR 23A is critical for cell cycle arrest induced by Vpr. These results pr ovide further support for the hypothesis that Vpr interferes with the normal function of a protein or proteins involved in the DNA repair pr ocess and, thus, in the transmission of signals that allow cells to tr ansit from the G(2) to the M phase of the cell cycle.