<p>This entry represents transcription elongation factors of the IIS type. TFIIS is a component of RNA polymerase II preinitiation complexes, and is required for preinitiation complex assembly and stability [<cite idref="PUB00042911"/>]. The association of TFIIS with a promoter depends on functional preinitiation complex components including Mediator and the SAGA complex [<cite idref="PUB00042912"/>]. TFIIS is composed of three domains: domain 1 forms a 4-helical bundle that appears to bind certain initiation factors; domain 2 forms a 3-helical bundle and is required for Pol II binding; domain 3 forms a zinc ribbon and is essential for stimulation of RNA cleavage [<cite idref="PUB00042913"/>, <cite idref="PUB00042914"/>].</p>