THIS PAPER HAS BEEN RETRACTED. For full details, please see the associated retraction, FBrf0105924. Data in Figs. 5 and 6 are incorrect and those in Figs. 7-9 are uncertain and have been removed from FlyBase. The isolation and molecular characterization of the TAFII mutants in Figs. 1-3 is correct and these data remain associated with the original paper in FlyBase.