text: The expressome is a supramolecular complex consisting of RNA polymerase and a trailing ribosome linked by a shared mRNA transcript. It is supported by the transcription factors NusG and NusA, which interact with both RNA polymerase and the ribosome to couple the complexes together. When coupled by transcription factor NusG, the ribosome binds newly synthesized mRNA and prevents formation of secondary structures that inhibit transcription. Formation of an expressome complex also aids transcription elongation by the trailing ribosome opposing back-tracking of RNA polymerase. Three-dimensional models of ribosome-RNA polymerase expressome complexes have been determined by cryo-electron microscopy.