Rrn7 from yeast and its orthologue TATA box-binding protein-associated factor RNA polymerase I subunit B (TAF1B) from human, are TFIIB-like factors components of RNA polymerase I core factor complex. They contain two cyclin fold domains. In Rrn7 the cyclin domains interact with both Rrn6 and Rrn11 and form the fingers of the core factor which resembles a right hand. N-terminal regions of both Rrn11 and Rrn6 compose the palm, the thumb is composed by the C-terminal of Rrn11 and the knuckles consist of the C-terminal half of Rrn6. This is the C-terminal cyclin domain of Rrn7 from yeast and the orthologues from animals and plants TAF1B [1,2].

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