14-3-3 theta binding to cell cycle regulatory factors is enhanced by HIV-1 Vpr.

Despite continuing advances in our understanding of AIDS pathogenesis, the mechanism of CD4+ T cell depletion in HIV-1-infected individuals remains unclear. The HIV-1 Vpr accessory protein causes cell death, likely through a mechanism related to its ability to arrest cells in the G2,M phase. Recent evidence implicated the scaffold protein, 14-3-3, in Vpr cell cycle blockade. We found that in human T cells, 14-3-3 plays an active role in mediating Vpr-induced cell cycle arrest and reveal a dramatic increase in the amount of Cdk1, Cdc25C, and CyclinB1 bound to 14-3-3 theta during Vprv-induced G2,M arrest. By contrast, a cell-cycle-arrest-dead Vpr mutant failed to augment 14-3-3 theta association with Cdk1 and CyclinB1. Moreover, G2,M arrest caused by HIV-1 infection strongly correlated with a disruption in 14-3-3 theta binding to centrosomal proteins, Plk1 and centrin. Finally, Vpr caused elevated levels of CyclinB1, Plk1, and Cdk1 in a complex with the nuclear transport and spindle assembly protein, importin beta. Thus, our data reveal a new facet of Vpr-induced cell cycle arrest involving previously unrecognized abnormal rearrangements of multiprotein assemblies containing key cell cycle regulatory proteins.