Multiple viral strategies of HTLV-1 for dysregulation of cell growth control

The human T cell leukemia virus-1 (HTLV-1) is a retrovirus that causes adul t T cell leukemia (ATL) and neurological disorder, the tropical spastic par aparesis (HAM/TSP). The pathogenesis apparently results from the pleiotropi c function of Tax protein, which is a key regulator of viral replication. T ax exerts (a) trans-activation and -repression of transcription of differen t sets of cellular genes through binding to groups of transcription factors and coactivators, (b) dysregulation of cell cycle through binding to inhib itors of CDK4/6, and (c) inhibition of some tumor suppressor proteins. Thes e effects on a wide variety of cellular targets seem to cooperate in promot ing cell proliferation. This is an effective viral strategy to amplify its proviral genome through replication of infected cells; ultimately it result s in cell transformation and leukemogenesis.