Involved in RNA polymerase III-mediated transcription. Integral, tightly associated component of the DNA-binding TFIIIC2 subcomplex that directly binds tRNA and virus-associated RNA promoters. Part of the TFIIIC subcomplex TFIIIC2, consisting of six subunits, GTF3C1, GTF3C2, GTF3C3, GTF3C4, GTF3C5 and GTF3C6. Interacts with GTF3C4 and GTF3C5. Belongs to the TFIIIC subunit 6 family.