Kinase-Inducible Domain-Like Region of HTLV Type 1 Tax Is Important for NF- κ B Activation

Abstract

Partial proteolysis of HTLV-1 Tax protein has revealed the region surrounding amino acid residues ₈₈KVL₉₀ to be highly exposed. The protein sequence surrounding this region (₈₁QRTSKTLKVLTPPIT₉₅) bears resemblance to the kinase-inducible domain (KID, ₁₂₉SRRPSYRKILNE₁₄₀) of CREB and is involved in recruiting transcriptional coactivators, p300 and CBP, for trans-activating the viral long terminal repeat (LTR). Data have also revealed the KID-like region to be important for Tax binding to DNA. Here we report that single (K88A, V89A, L90A) and double alanine substitutions (V89A-L90A) in the ₈₈KVL₉₀ motif attenuate the ability of Tax to activate NF-κB. Deletions near or spanning this motif also had the same effect. The alanine substitutions affect HTLV-1 LTR activation and NF-κB activation differently, with K88A and V89A mutants showing much reduced activities for HTLV LTR activation while retaining attenuated but significant NF-κB-activating function. In contrast, although the L90A mutant is similarly attenuated for NF-κB activation, it showed significant activity in LTR trans-activation. Incorporation of both V89A and L90A substitutions in a V89A-L90A double mutant further reduced NF-κB activation and completely abrogated LTR trans-activation. In aggregate, these results demonstrate the importance of the KID-like domain of Tax and implicate its interaction with cellular factors other than p300/CBP in NF-κB activation.