cd13749

domain III/zinc ribbon domain of Transcription Factor IIS; TFIIS is a zinc-containing transcription factor. It has been shown in vitro to have distinct biochemical activities, including binding to RNA polymerases, stimulation of transcript elongation, and activation of a nascent RNA cleavage activity in the RNA polymerase II (Pol II) elongation complex. TFIIS consists of three domains. Domain II and III are sufficient for all known TFIIS activities. Domain III is a zinc ribbon that separated from domain II by a long linker and is indispensable for TFIIS function. The TFIIS homologs, subunits A12.2, B9, and C11, of Pol I, II, and III respectively, are required for RNA cleavage by the polymerases. In a single organism, there are tissue-specific TFIIS related proteins.