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RNA polymerase III is part of the transcription machinery of eukaryotes. It handles genes encoding for small structured RNAs: tRNA, spliceosomal U6 snRNA and 5S rRNA. RNA polymerase III is the largest eukaryotic RNA polymerase, yet it is the least characterized.

Elongation is the process of adding nucleotides to a growing RNA strand.

RNA Polymerase III is composed of mobile elements which move relative to each other. Conformational changes result in the complex, which

This page catalogs subunits of RNA Polymerase III which are relevant to elongation complex transcription.

Function

Pol III

The RPC25/RPC8-RPC17/RPC9 subcomplex binds the transcripts emerging from the exit pore, which facilitates elongation.

Interactions

RPC2 contributes to catatylic activity in the polymerase, and forms the active center of the polymerase along with the largest subunit. It is suggested that RPC helps to open and close the cleft.

RPC1 forms active center together with RPC2

forms a bridging helix that crosses the cleft near the active site, acts as a ratchet that moves the enlongating transcript through polIII

The of the polymerase moves the DNA by bridging helix, which allows transcription to proceed. This takes place by a ratcheting motion. It promotes translocation of polIII by allowing nucleotides to be added continuously

RPC6 recruits pol III to the preinitiation complex, and contributes to an initiation-competent configuration for pol III

RPC4 is needed for tRNA synthesis!!

The RPC53/RPC4-RPC37/RPC5 subcomplex functions to terminate transcription and reinitiate transcription, by providing a binding site for the terminator.

RPAC1 helps to open and close the cleft

RPC10 involved in transcription reinitiation and RNA cleavage during termination

Origin

A 2015 deposition to PDB by Hoffman et al used electron cryomicroscopy to elucidate the structure shown on this page, came from Saccharomyces cerevisiae. Tihs

Structural highlights