Interaction between yeast RNA polymerase III and transcription factor TFIIIC via ABC10 alpha and tau 131 subunits

Yeast TFIIIC mediates transcription of class III genes by promoting the ass embly 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, tau 131, and ABC10 alpha, a small essential subunit common to the three forms of nuclea r RNA polymerases. This interaction was mapped to the C-terminal region of ABC10 alpha. A thermosensitive mutation in the C terminus region of ABC10 a lpha (rpc10-30) was found to be selectively suppressed by overexpression of a mutant form of tau 131 (tau 131-Delta TPR2) that lacks the second TPR re peat. Remarkably, the rpc10-30 mutation weakened the ABC10 alpha-tau 131 in teraction, and the suppressive mutation, tau 131-Delta TPR2 increased the i nteraction between the two proteins in the two-hybrid assay. These results point to the potential importance of a functional contact between TFIIIC an d RNA polymerase III.