Component of RNA polymerase I core factor complex that acts as a GTF2B/TFIIB-like factor and plays a key role in multiple steps during transcription initiation such as pre-initiation complex (PIC) assembly and postpolymerase recruitment events in polymerase I (Pol I) transcription. Binds rDNA promoters and plays a role in Pol I recruitment (By similarity). Although it shares weak sequence similarity with GTF2B/TFIIB, displays a similar subdomain organization as GTF2B/TFIIB, with a N-terminal zinc finger, a connecting region (composed of B-reader and B-linker regions), followed by 2 cyclin folds. The RRN7-type zinc finger plays an essential postrecruitment role in Pol I transcription at a step preceding synthesis of the first 40 nucleotides (By similarity). Belongs to the RRN7/TAF1B family.