Abstract
We have subdivided the components of the basic RNA polymerase II machinery from Drosophila embryos into three fractions and RNA polymerase II. The RNA polymerase II was 90% homogeneous and possessed the IIa form of the largest subunit. By substitution of these factors with their mammalian homologues in reconstituted transcription reactions, we have determined that the three Drosophila fractions contain transcription factor (TF)IIB, TFIIE/F, and TFIID. In addition, the fraction with TFIID contains another essential activity, which we have tentatively designated as TFIIZ. There was no apparent requirement for TFIIA. The reconstituted transcription factors accurately transcribe both Drosophila and mammalian genes. This fractionated system should serve as a source of general transcription factors for the study of RNA polymerase II transcription in Drosophila as well as other eukaryotes.
