INTERACTIONS BETWEEN HTLV-I TAX AND NF-KAPPA-B REL PROTEINS IN T-CELLS/

Members of e NF-kappa B/Rel family of transcription factors are involv ed in the transcriptional regulation of numerous polypeptides importan t to the immune response and cellular growth. Several genes regulated in part by NF-kappa B/Rel such as interleukin 2, IL-2 receptor alpha, and GM-CSF are trans-activated via an indirect association with the HT LV-I Tax protein in virus infected and transformed T cells. In this st udy, we have investigated the interactions between Tax and NF-kappa B/ Rel in an attempt to elucidate the mechanism of Tax mediated trans-act ivation and its role in leukemogenesis. Transfection studies were perf ormed in Jurkat T cells using expression vectors for individual NF-kap pa B subunits and the Tax protein as well as an NF-kappa B regulated r eporter plasmid. NF-kappa B proteins differentially trans-activated th e HIV-1. enhancer-CAT reporter; co-expression of Tax abrogated the inh ibitory effect of I kappa B alpha and a trans-dominant negative mutant of p65 (p65 Delta), indicating that Tax was a trans-dominant activato r of NF-kappa B-regulated genes. Co- immunoprecipitation studies with extracts from transfected cells and NF-kappa B and Tax subunit specifi c antibodies revealed that Tax did not co-immunoprecipitate with p50/p 105, c-Rel, or I kappa B; however, antibody specific to p65 was able t o co-immunoprecipitate a 40kDa protein Tax-transfected cells. Previous studies demonstrated a physical interaction between Tax protein and p 100, indicating that Tax may preferentially associate with specific NF -kappa B proteins.