人类T淋巴细胞1型病毒HTLV-1 TAX通过持续性激活IKK-NF-κB信号通路导致成人T细胞白血病ATL。TAX持续性激活IKK的生化机制函待深入研究。为避免现有细胞和动物水平上研究的局限，我们发展了基于TAX激活IKK的体外无细胞系统。该系统避免了TAX激活的多种信号通路和IKK-NF-κB正反馈通路叠加在一起而无法分割的情况。利用该系统，我们将1）使用经典液相色谱蛋白纯化系统来分离纯化TAX激活IKK所需的宿主因子，2）探讨这些因子与TAX共同激活IKK的深入机制，3）探讨TAX自身的生化功能，4）TAX抑制A20、CYLD去泛素化酶活性以及A20、CYLD的诱导表达达到持续性激活IKK的机制。对TAX激活IKK机制的研究将有助于我们一方面深入理解TAX以及HTLV-1病毒引起肿瘤的原因，另一方面深入理解慢性炎症NF-κB通路持续性激活在肿瘤生成中扮演的重要功能。

Human T-cell lymphotropic virus type 1(HTLV-1) has been characterized as the etiological agent of adult T-cell leukemia/lymphoma (ATL) and HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). HTLV-1 encodes a 40-KD regulatory protein, TAX, that can activate various intracellular signaling pathways including IKK/NF-kB, PI3K/AKT and SRF pathways, among which IKK/NF-kB signaling pathway is thought to be critical in onset of ATL. A lot of studies have been focused on the mechanism of TAX-mediated activation of IKK/NF-kB; however, exactly how TAX activates IKK is still a mystery and further studies are needed.. To understand exactly how IKK is activated by TAX, we used an in vitro cell-free system to reconstitute TAX-dependent IKK activation. Using this assay, our fractionation studies revealed that several factors are required for IKK activation by TAX. One factor was further fractionated, purified and identified by mass spectrometry as the ubiquitin conjugating enzyme E2 UBE2L3 (UbcH7). Screening of recombinant E2s using the cell-free system showed that two other E2s, UBE2H (UbcH2) and UBE2D3 (UbcH5c), can confer TAX-dependent IKK activation. The importance of these E2s in supporting TAX-dependent IKK activation was further verified in vivo by using dominant negative forms of these E2s, which inhibit TAX-dependent NF-kB activation when overexpressed.. We also characterized the requirement of TAK1, Ubc13 and TRAF6 for IKK activation by TAX, which have been controversial in the literature. Our both in vitro and in vivo studies revealed that neither TAK1, TRAF6 nor Ubc13 is involved in TAX-dependent IKK activation.. TAX-dependent IKK activation might provide probably the simplest system to understand biochemical mechanism of IKK activation and understanding the mechanism might also help us find therapies to ATL. Further studies are underway to elucidate the detailed biochemical mechanism of IKK activation by TAX.