This gene encodes the small subunit of DRB (5,6-dichloro-1-beta-d-ribofuranosylbenzimidazole) sensitivity-inducing factor (DSIF) complex, which regulates mRNA processing and transcription elongation by RNA polymerase II. The encoded protein is localized to the nucleus and interacts with the large subunit (SUPT5H) to form the DSIF complex. Related pseudogenes have been identified on chromosomes 2 and 12. Alternatively spliced transcript variants have been found for this gene. [provided by RefSeq, Nov 2012]