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. {ECO:0000269|PubMed:11250903, ECO:0000269|PubMed:11283244, ECO:0000269|PubMed:15970593, ECO:0000269|PubMed:21921198, ECO:0000269|PubMed:21921199, ECO:0000269|PubMed:7491500, ECO:0000269|PubMed:7801123, ECO:0000269|PubMed:7801130}. This is the function of Ensembl gene identifier ENSG00000115750 (TAF1B, TATA-box binding protein associated factor, RNA polymerase I subunit B).