RNA polymerases are unable to initiate RNA synthesis in the absence of additional proteins called general transcription factors (GTFs). GTFs assemble in a complex on the DNA promoter and recruit the RNA polymerase. GTF3C family proteins (e.g., GTF3C1, MIM 603246) are essential for RNA polymerase III to make a number of small nuclear and cytoplasmic RNAs, including 5S RNA (MIM 180420), tRNA, and adenovirus-associated (VA) RNA of both cellular and viral origin.[supplied by OMIM, Mar 2008].