HTLV-1 Tax [1A3]

The Human T-lymphotropic virus Type I (HTLV-1) is a human RNA retrovirus that causes T-cell leukemia/lymphoma (ATL) in adults and may also be involved in certain demyelinating diseases, including tropical spastic paraparesis. The HTLV-1 genome is diploid, composed of two copies of a single-stranded RNA virus whose genome is copied into a double-stranded DNA form that integrates into the host cell genome, at which point the virus is referred to as a provirus. The glycoproteins encoded by the env gene of HTLV-1 are essential for interaction with an unidentified receptor on the surface of target cells and play a crucial role in the infection process. Encoded by HTLV-1 Tax is a phospho-oncoprotein that functions as a transcriptional activator. Tax has the ability to modulate the expression and function of many cellular genes and has been crucial to understanding the HTLV-1-mediated transformation of cells. In activating cellular gene expression, Tax impinges upon several cellular signal-transduction pathways, including the CREB/ATF and NFkB pathways. In addition, Tax deregulates the expression of downstream genes, which mediate cell cycle control.