This is the helical bundle domain (also referred to as the headlock domain) of TATA box-binding protein-associated factor RNA polymerase I subunit C (TAF1C) from animals, the orthologue of yeast Rrn6 [1,2]. TAF1C is a component of the transcription factor SL1/TIF-IB complex, which is involved in the assembly of the PIC (preinitiation complex) during RNA polymerase I-dependent transcription [3].

1: Structural Basis of RNA Polymerase I Transcription Initiation. Engel C, Gubbey T, Neyer S, Sainsbury S, Oberthuer C, Baejen C, Bernecky C, Cramer P; Cell. 2017;169:120-131. PMID:28340337

2: Structural mechanism of ATP-independent transcription initiation by RNA polymerase I. Han Y, Yan C, Nguyen THD, Jackobel AJ, Ivanov I, Knutson BA, He Y; Elife. 2017; [Epub ahead of print] PMID:28623663

3: TBP-TAF complex SL1 directs RNA polymerase I pre-initiation complex formation and stabilizes upstream binding factor at the rDNA promoter. Friedrich JK, Panov KI, Cabart P, Russell J, Zomerdijk JC; J Biol Chem. 2005;280:29551-29558. PMID:15970593