General activator of RNA polymerase III transcription. Requires for transcription from all three types of polymerase III promoters. Requires for transcription of genes with internal promoter elements and with promoter elements upstream of the initiation site (By similarity). Component of TFIIIB complex. The TFIIIB complex has two activities, alpha and beta. The TFIIIB-alpha and TFIIIB-beta activities are required for transcription of genes with TFIIIC-bound internal promoters and PSE transcription factor-bound external promoters, respectively. The TFIIIB-alpha activity complex is composed of TBP, BDP1, and a complex containing both BRF2 and at least four stably associated proteins; YY1 facilitates the formation of TFIIIB-alpha activity complex. The TFIIIB-beta activity complex is composed of TBP, BDP1, and BRF1. Interacts with BRF1; this interaction diminishes during mitosis resulting in the release of BDP1 from chromosomal templates. Component of TFIIIC complex. The TFIIIC complex has two activities, C1 and C2. The TFIIIC2 activity complex is only required for transcription of the 'classical' pol III genes whereas the TFIIIC1 activity complex is required for transcription of all pol III genes. The TFIIIC1 activity complex is composed at least of BDP1. Interacts with ZBTB43 (By similarity). Expressed in the cochlea, particularly in the spiral ligament, the capillaries of the stria vascularis and the basilar membrane. Phosphorylated by CSNK2A1 during mitosis, resulting in its release from chromatin and suppression of polymerase III transcription. Contaminating sequence. Sequence of unknown origin in the N-terminal part.