NELF (Negative elongation factor) is a four subunit protein (NELF-A, NELF-B, NELF-C or NELF-D, NELF-E) that affects transcription by RNA polymerase II. Subunit NELF-E is also known as RDBP.[1][2] The NELF-A subunit is encoded by the gene WHSC2, Wolf-Hirschhorn syndrome candidate 2. NELF-C and NELF-D are probably peptides resulting from the same mRNA with different translation initiation site, possibly differing only in an extra 9 amino acids for NELF-C at the N-terminus. Or, it is possible they arise from different mRNAs. A single NELF complex consists of either NELF-C or NELF-D but not both. Microsequencing analysis showed that NELF-B was the protein previously identified as the protein encoded by the gene COBRA1, and shown to interact with BRCA1.[2]
NELF binds in a stable complex with DSIF and RNA Polymerase II together, but not with either alone. P-TEFb inhibits the effect of NELF and DSIF on Pol II elongation, via its phosphorylation of Serine 2 on the C-terminal domain of Pol II, and the SPT5 subunit of DSIF, causing dissociation of NELF.[2] NELF homologues exist in some metazoans (e.g. insects and vertebrates) but have not been found in plants, yeast, or nematode (worms).[2]