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Abstract:
Transcription initiation by eukaryotic RNA polymerase (Pol) III relies
on the TFIIE-related subcomplex C82/34/31. Here we combine crosslinking
and hydroxyl radical probing to position the C82/34/31
subcomplex around the Pol III active center cleft. The extended
winged helix (WH) domains 1 and 4 of C82 localize to the polymerase
domains clamp head and clamp core, respectively, and the two WH
domains of C34 span the polymerase cleft from the coiled-coil region
of the clamp to the protrusion. The WH domains of C82 and C34
apparently cooperate with other mobile regions flanking the cleft
during promoter DNA binding, opening, and loading. Together with
published data, our results complete the subunit architecture of Pol
III and indicate that all TFIIE-related components of eukaryotic and
archaeal transcription systems adopt an evolutionarily conserved
location in the upper part of the cleft that supports their functions in
open promoter complex formation and stabilization.
