Control of transcription by Krüppel through interactions with TFIIB and TFIIE beta.

The zinc-finger protein Krüppel (Kr) is an integral part of the Drosophila segmentation gene cascade and is essential in organogenesis during later embryonic development. In tissue culture, Kr regulates transcription. Monomeric Kr can act as a transcriptional activator, whereas Kr dimers formed at high concentrations cause repression. Here we show that Kr-dependent control of transcription involves functional interactions with components of the basal RNA polymerase II transcription machinery, which includes the initiation factors TFIIA, B, E, F, H and I (refs 10, 11) as well as the TATA-binding protein (TBP) and TBP-associated factors (TAFs) contained in the multisubunit TFIID (ref. 12). Our results indicate that when acting from a site close to a basal promoter, monomeric Kr interacts with TFIIB to activate transcription, whereas an interaction of the Kr dimer with TFIIE beta, a subunit of TFIIE, results in transcriptional repression.