High Quality Content by WIKIPEDIA articles! Cofactor of BRCA1, also known as COBRA1, is a human gene that encodes NELF-B. NELF-B is a subunit of negative elongation factor (NELF), which also includes NELF-A (WHSC2; MIM 606026), either NELF-C or NELF-D (TH1L; MIM 605297), and NELF-E (RDBP; MIM 154040). NELF acts with DRB sensitivity-inducing factor (DSIF), a heterodimer of SPT4 (SUPT4H1; MIM 603555) and SPT5 (SUPT5H; MIM 602102), to cause transcriptional pausing of RNA polymerase II (see MIM 180660). COBRA1 was initially identified in a yeast two-hybrid screen using the BRCT1 domain of BRCA1 as bait.