FIG. 5.

Immunodepletion of CAK from holo-TFIIH with anti-Mat1 antibodies does not affect Tat activation. Immobilized anti-Mat1 antibodies were used to immunodeplete Mat1 from HeLa nuclear extract containing 0.8 M KCl. Immobilized anti-Myc MAb was used in a control depletion reaction. (A) The depleted extracts were analyzed for their abilities to mediate Tat activation in transcription reactions as described in the legend for Fig. 1. (B) The removal of Mat1 and its associated Cdk7 in the CAK complex was confirmed by Western blotting with anti-Mat1 and anti-Cdk7 antibodies.