RNA polymerase I is a multisubunit enzyme and its transcription competence is dependent on the presence of PAF67 [1]. This family of proteins is conserved from worms to humans.

1: PAF67, a novel protein that is associated with the initiation-competent form of RNA polymerase I. Seither P, Iben S, Thiry M, Grummt I; Biol Chem. 2001;382:1163-1170. PMID:11592397