Rpb7 bind to Rpb4 to form a heterodimer. This complex is thought to interact with the nascent RNA strand during RNA polymerase II elongation[1]. This family includes the homologs from RNA polymerase I and III. In RNA polymerase I, Rpa43 is at least one of the subunits contacted by the transcription factor TIF-IA [2]. The N terminus of Rpb7p/Rpc25p/MJ0397 has a SHS2 domain that is involved in protein-protein interaction [3].

1: Structure of an archaeal homolog of the eukaryotic RNA polymerase II RPB4/RPB7 complex. Todone F, Brick P, Werner F, Weinzierl RO, Onesti S; Mol Cell 2001;8:1137-1143. PMID:11741548

2: Multiple interactions between RNA polymerase I, TIF-IA and TAFI subunits regulate preinitiation complex assembly at the ribosomal gene promoter. Yuan X, Zhao J, Zentgraf H, Hoffmann-Rohrer U, Grummt I; 0;0:1-2. PMID:12393749

3: The SHS2 module is a common structural theme in functionally diverse protein groups, like Rpb7p, FtsA, GyrI, and MTH1598/TM1083 superfamilies. Anantharaman V, Aravind L; Proteins. 2004;56:795-807. PMID:15281131