Fig. 1. vFLIP interacts directly with the IKK subunit of the IKK complex. A human placental cDNA library was screened for proteins interacting with a vFLIP bait using yeast-two-hybrid technology. (A) A schematic representation of IKK with a list of the six independent fusions of IKK (B). Black boxes indicate coiled-coil regions (CCR), white boxes indicate the leucine zipper domains (LZ) essential for interaction of HTLV-1 Tax with IKK and the grey box indicates a zinc finger motif (ZF). The N-terminus of IKK is responsible for interaction with IKK and ß, whereas the C-terminus is required for activation of the IKK complex. Truncation mutants of IKK, generated as Xpress tag or GST fusions, are shown (C). (D) The interaction of Xpress tagged IKK truncation mutants with vFLIP when both are overexpressed in 293T cells. Cell lysates were immunoprecipitated using an anti-vFLIP antibody and analysed by immunoblot probed with an anti-Xpress antibody. (E) Interaction of vFLIP transiently expressed in 293T cells with GST fusion IKK mutants.