Identification of genes that are regulated by TAK1 in human cutaneous T cell lymphoma HuT-102 cells

We previously reported that human T cell lymphotropic virus 1 (HTLV-1) Tax oncoprotein constitutively activates TAK1. Here, we established Tax-positive HuT-102 cells stably downregulated TAK1 expression by short-hairpin RNA (HuT-shTAK1 cells), and investigated the physiological function of TAK1. Microarray analysis demonstrated that several interferon (IFN)-inducible genes including chemokines such as CXCL10 and CCL5 were significantly downregulated in HuT-shTAK1 cells. In contrast, Tax-mediated constitutive activation of NF-kB was intact in HuT-shTAK1 cells. IRF3, a critical transcription factor in innate immunity to viral infection, was constitutively activated in a Tax-dependent manner. Activation of IRF3 and IRF3-dependent gene expression were dependent on TAK1 and TBK1. On the other hand, IRF4, another IRF family of transcription factor overexpressed in a Tax-independent manner, negatively regulated the TAK1-dependent IRF3 transcriptional activity. Together, HTLV-1 manipulates IFN signaling by regulating both positive and negative IRFs. HuT-102 cells, a human cutaneous T cell lymphoma, were stably transfected with shRNA expression vectors against human MAP3K7 (TAK1) or firefly luciferase (Luc). The cells were maintained in media containing 0.5 mg/ml G418. For the experiment, the cells were incubated in media without G418 for 36 h at 37°C. Total RNA samples were prepared from the cells. Gene expression was analyzed by an Affymetrix GeneChip® system with a Human Genome U133-plus 2.0 array for analysis of over 47,000 transcripts. Sample preparation for array hybridization was carried out as described in the manufacturer’s instructions. Two replicates per sample type.