SIII, also known as elongin, is a general transcription elongation factor that increases the RNA polymerase II transcription elongation past template-encoded arresting sites. Subunit A is transcriptionally active and its transcription activity is strongly enhanced by binding to the dimeric complex of the SIII regulatory subunits B and C (elongin BC complex).Aso T., Gene 168:277-278(1996).Gregory S.G., Nature 441:315-321(2006).Olsen J.V., Cell 127:635-648(2006)