BTF2/TFIIH from human, delta from rat, and factor b from yeast are multisubunit basal transcription factors that have been shown to be closely associated with a protein kinase capable of phosphorylating the carboxyl-terminal domain of the large subunit of RNA polymerase II (Lu, H., Zawel, L., Fischer, L., Egly, J. M., and Reinberg, D. (1992) Nature 358, 641-645; Serizawa, H., Conaway, R. C., and Conaway, J. W. (1992) Proc. Natl. Acad. Sci. U.S.A. 89, 7476-7480; Feaver, W. J., Gileadi, O., and Kornberg, R. D. (1991) Cell 67, 1223-1230). We report here that a DNA-dependent ATPase and the previously characterized helicase (Schaeffer, L., Roy, R., Humbert, S., Moncollin, V., Vermeulen, W., Hoeijmakers, J., Chambon, P., and Egly, J. M. (1993) Science 260, 58-63) are both associated with BTF2 and reside with the p89 polypeptide subunit. The DNA requirement, the effect of Sarkosyl and staurosporine inhibitors, as well as nucleotide competition experiments, clearly distinguished ATPase/helicase from the carboxyl-terminal domain kinase. Using recombinant wild type or mutated p89/ERCC3 polypeptides and different forms of DNA template, we show the connection between ATPase and the helicase.