COBRA1 (Cofactor of BRCA1) is also known as NELFB (negative elongation factor E). NELFB is one of four subunits that make up the NELF transcription elongation factor. The four subunits of NELF are NELF A (WHSC2), NELFB, either NELFC or NELFD, and NELFE. NELF, along with DRB sensitivity-inducing factor (DSIF), functions to cause transcriptional pausing of RNA polymerase II. COBRA1 was originally identified in a yeast two-hybrid screen of a human ovary cDNA library using the BRCA COOH terminus repeat, BRCT1, as the bait protein. In this study, COBRA1 was found to be involved in BRCT1-mediated chromatin remodeling. COBRA1 has also been found to interact with several nuclear receptors such as ERalpha and androgen receptor to modulate their transcriptional activity.