This gene encodes the transcriptionally active subunit of the SIII (or elongin) transcription elongation factor complex, which also includes two regulatory subunits, elongins B and C. This complex acts to increase the rate of RNA chain elongation by RNA polymerase II by suppressing transient pausing of the polymerase at many sites along the DNA template. Whereas a related protein with similar function, elongin A, is ubiquitously expressed, the encoded protein is specifically expressed in the testis, suggesting it may have a role in spermatogenesis. [provided by RefSeq, Jul 2008].