Transcribing RNA polymerase III observed by electron cryomicroscopy.

Electron cryomicroscopy reconstructions of elongating RNA polymerase (Pol) III at 3.9 Å resolution and of unbound Pol III (apo Pol III) in two distinct conformations at 4.6 Å and 4.7 Å resolution allow the construction of complete atomic models of Pol III and provide new functional insights into the adaption of Pol III to fulfill its specific transcription tasks.