Macromolecular Electron Microscopy Studies of the Eukaryotic Transcription Machinery

Abstract

Transcription is the process in which genetic information encoded in DNA is translated to messenger RNA, which is then used to direct protein synthesis. Precise regulation of transcription underlies cell development and differentiation, and modulates the response of the cell to external factors. Problems with transcription regulation are responsible for a number of human pathologies, most notably cancer. In eukaryotic cells, the basal transcription machinery comprises RNA polymerase II (RNAPII) and its associated general transcription factors. Regulation requires the intervention of a large number of macromolecular complexes, which alter chromatin structure to modulate access to specific portions of the genome, and convey regulatory information to the basal machinery during the transcription initiation process. Although a great deal remains to be understood about the mechanism of transcription regulation, the Mediator complex (first identified in yeast and now detected in humans and other metazoans) seems to play a key role in transducing regulatory information to the basal machinery.