Roles of Vpr and Vpx in modulating the virus-host cell relationship

The human and simian immunodeficiency viruses contain small open reading frames known as vpr and vpx. These genes encode proteins that are highly related both at the amino acid level and functionally, although key differences do exist. This review describes the main functions ascribed to Vpr and Vpx in the context of both viral replication and modulation of host cell biology.