Activates transcription elongation by RNA polymerase II and pyrophosphorolysis as a complex with eaf1. Elongation factor that can increase the catalytic rate of RNA polymerase II transcription by suppressing transient pausing by the polymerase at multiple sites along the DNA. Forms a stable heterodimer with eaf1. Ell1-eaf1 complex interacts with RNA polymerase II. Deletion of ell1 renders cells sensitive to the drug 6-azauracil. Belongs to the ELL/occludin family.