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 as a component of the SL1/TIF-IB complex and, possibly, directly through its interaction with RRN3 (By similarity). Interacts with FLNA (via N-terminus) (By similarity). Component of the transcription factor SL1/TIF-IB complex, notably composed of TBP and at least TAF1A, TAF1B, TAF1C and TAF1D. In the complex interacts directly with TBP, TAF1A and TAF1C. Interaction of the SL1/TIF-IB subunits with TBP excludes interaction of TBP with the transcription factor IID (TFIID) subunits. Interacts with TBP and RRN3 (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.