Interaction between Yeast RNA Polymerase III and Transcription Factor TFIIIC via ABC10α and τ131 Subunits

Yeast TFIIIC mediates transcription of class III genes by promoting the assembly of a stable TFIIIB-DNA complex that is sufficient for RNA polymerase III recruitment and function. Unexpectedly, we found an interaction in vivo and in vitro between the TFIIIB-recruiting subunit of TFIIIC, τ131, and ABC10α, a small essential subunit common to the three forms of nuclear RNA polymerases. This interaction was mapped to the C-terminal region of ABC10α. A thermosensitive mutation in the C terminus region of ABC10α ( rpc10-30 ) was found to be selectively suppressed by overexpression of a mutant form of τ131 (τ131-ΔTPR2) that lacks the second TPR repeat. Remarkably, the rpc10-30 mutation weakened the ABC10α-τ131 interaction, and the suppressive mutation, τ131-ΔTPR2 increased the interaction between the two proteins in the two-hybrid assay. These results point to the potential importance of a functional contact between TFIIIC and RNA polymerase III.