Regulation of HTLV-1 transcription and deregulated gene expression by the virally-encoded protein Tax

Human T-cell Leukemia Virus Type-1 (HTLV-1) is the etiological agent of Adult T-cell Leukemia/Lymphoma (ATLL) and Tropical Spastic Paraparesis/HTLV-1 Associated Myelopathy (TSP/HAM). In combination with other cellular transcription factors, the viral protein Tax activates transcription by interacting with the cellular transcription factor CREB, and the cellular coactivator CBP/p300. In addition to activating transcription, Tax has also been shown to disrupt many cellular processes that may lead to malignant transformation.;We have studied two possible mechanisms for the ability of Tax to deregulate cellular function. We identified a domain on CBP/p300 responsible for binding p53, and it competes with Tax for binding to this domain. Tax has also been shown to deregulate cellular transcription through its effect on the functions of the cellular NF-κB family of proteins. We have studied the mechanisms of Tax deregulation via the NF-κB proteins by focusing on the events that occur directly at the promoters of NF-κB-responsive genes. We found no direct ability of Tax to deregulate the function of NF-κB at the NF-κB responsive promoter.;HTLV-1 transcription is a complex process that requires many cellular transcription factors including Sp1. We characterized binding of Sp1 to the HTLV-1 promoter in vitro and in vivo. Sp1 activates transcription modestly in vitro and in vivo in the absence of Tax, and a double point mutation at the preferred Sp1 binding site strongly down-regulates basal level transcription. These studies suggest a role for Sp1 in basal, and Tax-independent transcription of HTLV-1.;There are no current treatments for HTLV-1, and the median survival rate for a person diagnosed with ATL is roughly six months. We designed and synthesized six Tax-directed polyamides specifically designed to block Tax binding to the HTLV-1 promoter. We found that four of these polyamides disrupt binding of the Tax/CREB complex in vitro, and that these same molecules also inhibit Tax-mediated transcription in vitro. However, of these four Tax/CREB-specific polyamides, only one polyamide appears to be uniquely Tax specific. We show that polyamides can enter the nuclei of HTLV-1 infected T-cells, and two of the four polyamides down-regulate virion production in these cells.