Fig. 5.

Proposed model to explain Zta-mediated gene repression of the CIITA promoter. (a) The active CIITA promoter is shown. Basal transcription factors are represented as white spheres and co-activators by the stippled oval. RNA polymerase II is represented by the black cloud, with transcription indicated by an arrow. (b) The ability of a non-DNA-binding form of Zta (filled oval) to repress expression of the CIITA promoter suggests that some repression can occur without direct DNA contact. The simplest model to account for this has the N-terminal part of Zta blocking the interaction of the basal transcription machinery.