Plant-specific TFIIB-related protein that may be involved in an intracellular signaling pathway between plastids and the nucleus (PubMed:12697827). May act as general transcription factor (GTF) of RNA polymerase I-dependent transcription and rRNA synthesis. Forms a ternary complex with TBP2 and the rDNA promoter region (PubMed:18668124). Localizes to the nucleus under conditions of proteasome inhibition. A number of isoforms are produced. According to EST sequences. Widely expressed. Ubiquinated. Subsequent degradation by the proteasome pathway.