TFIIIC mediates tRNA and 5S RNA gene activation by binding to intragenic promoter elements. Upstream of the transcription start site, TFIIIC assembles the initiation complex TFIIIB-TFIIIC-tDNA, which is sufficient for RNA polymerase III recruitment and function. Part of the tauB domain of TFIIIC that binds boxB DNA promoter sites of tRNA and similar genes. Plays a role in TFIIB assembly through its interaction with SPT15/TBP. Essential for cell viability. Heterodimer with TFC6. Component of the TFIIIC complex composed of TFC1, TFC3, TFC4, TFC6, TFC7 and TFC8. The subunits are organized in two globular domains, tauA and tauB, connected by a proteolysis-sensitive and flexible linker. Interacts with SPT15 and directly with TFC6. Present with 2070 molecules/cell in log phase SD medium.