Structure of a conserved domain common to the transcription factors TFIIS,elongin A, and CRSP70

TFIIS is a transcription elongation factor that consists of three domains. We have previously solved the structures of domains II and III, which stimu late arrested polymerase II elongation complexes in order to resume transcr iption. Domain I is conserved in evolution from yeast to human species and is homologous to the transcription factors elongin A and CRSP70. Domain I a lso interacts with the transcriptionally active RNA polymerase II holoenzym e and therefore, may have a function, unrelated to the previously described transcription elongation activity of TFIIS. We have solved the structure o f domain I of yeast TFIIS using NMR spectroscopy. Domain I is a compact fou r-helix bundle that is structurally independent of domains II and III of th e TFIIS. Using the yeast structure as a template, we have modeled the homol ogous domains from elongin A and CRSP70 and identified a conserved positive ly charged patch on the surface of all three proteins, which may be involve d in conserved functional interactions with the transcriptional machinery.