Structural highlights
Function
TAX_HTL1C Transcriptional activator that activates both the viral long terminal repeat (LTR) and cellular promoters via activation of CREB, NF-kappa-B, SRF and AP-1 pathways. Binds to three 21 bp repeat elements located within the LTRs, referred to as Tax-responsive elements (TRE). Binding to TRE requires the interaction with CREB1 and CREBBP. Also induces chromatin remodeling of proviral LTR-mediated gene expression by recruiting the histone acetyl transferases CREBBP and EP300 to the chromatin, which results in histone acetylation. Via its interaction with IKK regulatory subunit IKBKG, Tax-1 persistently stimulates I-kappa-B kinase (IKK), resulting in constitutive activation of the transcription factor NF-kappa-B. Induction of the nuclear expression of members of the NFkB family of transcription factors, which leads to up-regulated expression of many gene promoters containing NFkB motifs. These genes include those encoding IL2, IL15, IL2RA and IL15RA, leading to autocrine IL2/IL2RA and IL15/IL15RA loops. The resulting T-cell proliferation leads to malignant transformation and to the development of adult T-cell leukemia (ATL). IL13, known to be linked to leukemogenesis, is also up-regulated by Tax-1. Interaction with PDZ domain-containing proteins induce IL2-independent growth, which may be a factor in multi-step leukemogenesis. Inhibits the action of at least three cellular tumor suppressors p53/TP53, RB1 and DLG1, and suppresses their abilities to dictate apoptosis in primary cells. Required for viral replication (By similarity).
