Elongin B (also known as RNA polymerase II transcription factor SIII p18 subunit and transcription elongation factor B polypeptide 2) is an 18 kD member of the UbH family containing a ubiquitin-like domain. Elongin functions as a subunit of a general transcription elongation factor that increases RNA polymerase II transcription elongation past template-encoded arresting sites in the nucleus. The Elongin BC complex acts as adaptor to link Elongin A, VHL, WSB1 or SOCS1 with a module of CUL2 or CUL5 and RBX1 to form E3 ubiquitin ligases. The 10C4 monoclonal antibody recognizes the human elongin B protein and has been shown to be useful for Western blotting.