CDC73 is an RNA polymerase II accessory factor [1], and forms part of the Paf1 complex that has roles in post-initiation events [2]. More specifically, crystal structure analysis shows the C-terminus to be a Ras-like domain that adopts a fold that is highly similar to GTPases of the Ras superfamily. The canonical nucleotide binding pocket is altered in CDC73, and there is no nucleotide ligand, but it contributes to histone methylation and Paf1C recruitment to active genes. Thus together with Rtf1 it combines to couple the Paf1 complex to elongating polymerase [3]. The family has been added to the P-loop clan on the basis of the topology of the b-stranded core, and its similarity to Ras.

1: A novel collection of accessory factors associated with yeast RNA polymerase II. Wade PA, Werel W, Fentzke RC, Thompson NE, Leykam JF, Burgess RR, Jaehning JA, Burton ZF; Protein Expr Purif 1996;8:85-90. PMID:8812838

2: Cdc73p and Paf1p are found in a novel RNA polymerase II-containing complex distinct from the Srbp-containing holoenzyme. Shi X, Chang M, Wolf AJ, Chang CH, Frazer-Abel AA, Wade PA, Burton ZF, Jaehning JA; Mol Cell Biol 1997;17:1160-1169. PMID:9032243

3: A complex containing RNA polymerase II, Paf1p, Cdc73p, Hpr1p, and Ccr4p plays a role in protein kinase C signaling. Chang M, French-Cornay D, Fan HY, Klein H, Denis CL, Jaehning JA; Mol Cell Biol 1999;19:1056-1067. PMID:9891041

4: Cdc73 subunit of Paf1 complex contains C-terminal Ras-like domain that promotes association of Paf1 complex with chromatin. Amrich CG, Davis CP, Rogal WP, Shirra MK, Heroux A, Gardner RG, Arndt KM, VanDemark AP; J Biol Chem. 2012;287:10863-10875. PMID:22318720