Lacoste J, Lanoix J, Pepin N, Hiscott J
Abe Stern Cancer Research Laboratory, Lady Davis Institute for Medical Research, Sir Mortimer B. Davis-Jewish General Hospital, Montréal, Québec, Canada.
Leukemia. 1994 Apr;8 Suppl 1:S71-6.
Members of the NF-kappa B/Rel family of transcription factors are involved in the transcriptional regulation of numerous polypeptides important 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 HTLV-I Tax protein in virus-infected and transformed T cells. In this study, we have investigated the interactions between Tax and NF-kappa B/Rel in an attempt to elucidate the mechanism of Tax mediated trans-activation and its role in leukemogenesis. Transfection studies were performed in Jurkat T cells using expression vectors for individual NF-kappa B subunits and the Tax protein as well as an NF-kappa B regulated reporter plasmid. NF-kappa B proteins differentially trans-activated the HIV-1 enhancer-CAT reporter; co-expression of Tax abrogated the inhibitory effect of I kappa B alpha and a trans-dominant negative mutant of p65 (p65 delta), indicating that Tax was a trans-dominant activator of NF-kappa B-regulated genes. Co-immunoprecipitation studies with extracts from transfected cells and NF-kappa B and Tax subunit specific antibodies revealed that Tax did not co-immunoprecipitate with p50/p105, c-Rel, or I kappa B; however, antibody specific to p65 was able to co-immunoprecipitate a 40kDa protein from Tax-transfected cells. Previous studies have demonstrated a physical interaction between Tax protein and p100, indicating that Tax may preferentially associate with specific NF-kappa B proteins.
核因子κB/Rel转录因子家族成员参与众多对免疫应答和细胞生长至关重要的多肽的转录调控。部分受核因子κB/Rel调控的几个基因，如白细胞介素2、IL-2受体α和粒细胞-巨噬细胞集落刺激因子，在病毒感染和转化的T细胞中通过与HTLV-I Tax蛋白的间接结合而被反式激活。在本研究中，我们研究了Tax与核因子κB/Rel之间的相互作用，试图阐明Tax介导的反式激活机制及其在白血病发生中的作用。使用单个核因子κB亚基和Tax蛋白的表达载体以及一个受核因子κB调控的报告质粒，在Jurkat T细胞中进行了转染研究。核因子κB蛋白对HIV-1增强子-CAT报告基因有不同程度的反式激活作用；Tax的共表达消除了IκBα和p65的反式显性负突变体（p65δ）的抑制作用，表明Tax是核因子κB调控基因的反式显性激活剂。用转染细胞提取物以及核因子κB和Tax亚基特异性抗体进行的共免疫沉淀研究表明，Tax不能与p50/p105、c-Rel或IκB共免疫沉淀；然而，p65特异性抗体能够从Tax转染细胞中共免疫沉淀出一种40kDa的蛋白。先前的研究已经证明Tax蛋白与p100之间存在物理相互作用，表明Tax可能优先与特定的核因子κB蛋白结合。
