Human T-Cell Leukemia Virus type 1 (HTLV-I), a retrovirus that currently 10 to 20 million people are infected with, has been shown to be associated with the Adult T-cell Leukemia (ATLL) and HTLV-associated myelopathy-tropical spastic paraparesis (HAM/TSP). 1 After an extended period of time, 3-5% of those infected with HTLV-1 will develop ATLL or HAM/TSP. The viral Tax protein is thought to have involvement in the development of these diseases. The Tax protein inhibits telomerase and topoisomerase-I which in turn inhibits the process of DNA repair. Tax prevents apoptosis and does not allow cells to enter the G0 phase of mitosis. The oncogenic properties of Tax are correlated to the interaction of Tax with host cellular proteins which are strongly influenced by the large amount of Tax protein made from the integrated provirus. We are using viral promoter magnetic pull-downs to investigate HTLV viral-host interactions involving minimal -306bp viral promoter containing vCRE enhancer sites and Tax-recruited host proteins. Experiments have used electrophoresis to determine whether or not the magnetic beads bind the promoter DNA. Absolute quantitation is necessary for consistency and reproducibility in analysis of proteins suspected of recruitment to the promoter.