Required for efficient transcription initiation by RNA polymerase I. Required for the formation of the competent preinitiation complex (PIC). Dissociates from pol I as a consequence of transcription. In vitro, cannot activate transcription in a subsequent transcription reaction (By similarity). Interacts with POLR1F, EIF3L, TAF1B and TAF1C. Phosphorylation is required for participation in rDNA transcription (By similarity). Phosphorylated at Thr-200 by MAPK9/JNK2, which abrogates initiation complex formation. Belongs to the RRN3 family.