Interaction between yeast RNA polymerase III and transcription factor TFIIIC via ABC10alpha and tau131 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, tau131, and ABC10alpha, a small essential subunit common to the three forms of nuclear RNA polymerases. This interaction was mapped to the C-terminal region of ABC10alpha. A thermosensitive mutation in the C terminus region of ABC10alpha (rpc10-30) was found to be selectively suppressed by overexpression of a mutant form of tau131 (tau131-DeltaTPR2) that lacks the second TPR repeat. Remarkably, the rpc10-30 mutation weakened the ABC10alpha-tau131 interaction, and the suppressive mutation, tau131-DeltaTPR2 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.