ELL2 (RNA polymerase II elongation factor ELL2) is a 640 amino acid nuclear protein that belongs to the ELL/occludin family. This family is defined by a highly conserved domain of approximately 100 amino residues found within all eukaryotic occludin proteins and the RNA polymerase II elongation factor ELL. These elongation factors activate elongation by suppressing transient pausing by polymerase at many sites along the DNA and govern its interaction with RNA polymerase II and the ternary elongation complex. ELL2 may also contain a novel type of RNA polymerase II interaction domain that is capable of negatively regulating polymerase activity in promoter-specific transcription initiation in vitro.