Coupling transcription and translation

In bacteria, the rate of transcription of messenger RNA (mRNA) by RNA polymerase (RNAP) is coordinated with the rate of translation by the first ribosome behind RNAP on the mRNA. Two groups now present cryo–electron microscopy structures that show how two transcription elongation factors, NusG and NusA, participate in this coupling. Webster et al. found that NusG forms a bridge between RNAP and the ribosome when they are separated by mRNA. With shortened mRNA, NusG no longer links RNAP and the ribosome, but the two are oriented so that newly transcribed mRNA can enter the ribosome. Wang et al. provide further insight into the effect of mRNA length on the complex structures. They also include NusA and show that the NusG-bridged structure is stabilized by NusA.
Science, this issue p. 1355, p. 1359


In bacteria, transcription and translation are coupled processes in which the movement of RNA polymerase (RNAP)–synthesizing messenger RNA (mRNA) is coordinated with the movement of the first ribosome-translating mRNA. Coupling is modulated by the transcription factors NusG (which is thought to bridge RNAP and the ribosome) and NusA. Here, we report cryo–electron microscopy structures of Escherichia coli transcription-translation complexes (TTCs) containing different-length mRNA spacers between RNAP and the ribosome active-center P site. Structures of TTCs containing short spacers show a state incompatible with NusG bridging and NusA binding (TTC-A, previously termed “expressome”). Structures of TTCs containing longer spacers reveal a new state compatible with NusG bridging and NusA binding (TTC-B) and reveal how NusG bridges and NusA binds. We propose that TTC-B mediates NusG- and NusA-dependent transcription-translation coupling.

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Supplementary Material


Materials and Methods
Figs. S1 to S16
Tables S1 and S2
References (2951)
Movies S1 to S11
MDAR Reproducibility Checklist


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Published In

Volume 369 | Issue 6509
11 September 2020

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Received: 1 March 2020
Accepted: 17 July 2020
Published in print: 11 September 2020


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We thank the Rutgers University Cryo-EM Core facility, the University of Michigan Life Sciences Institute Cryo-EM Facility, the National Center for Cryo-EM Access and Training (supported by NIH grant no. GM129539, Simons Foundation grant SF349247, and New York state grants), and the Pacific Northwest Center for Cryo-EM (supported by NIH grant no. GM129547 and Department of Energy Environmental Molecular Sciences Laboratory) for microscope access; K. Kuznedelov and K. Severinov for plasmids; L. Minakhin, B. Nickels, and J. Winkelman for discussion; and E. Eng and H. Wei for assistance. Funding: This work was supported by University of California discretionary funds to G.B., University of Michigan discretionary funds to M.S., and NIH grant no. GM041376 to R.H.E. Author contributions: V.M. and G.B. prepared biomolecules. C.W., V.M., E.F., J.K., and M.S. collected data. C.W., V.M., J.K., M.S., and R.H.E. analyzed data. C.W., V.M., and R.H.E. prepared figures. R.H.E. designed experiments and wrote the manuscript. Data and materials availability: Cryo-EM micrographs have been deposited in the Electron Microscopy Public Image Archive Resource (EMPIAR accession codes 10467 and 10468). Cryo-EM maps and atomic models have been deposited in the Electron Microscopy Database (EMDB accession codes 21386, 21468, 21469, 21470, 21471, 21472, 21474, 21475, 21476, 21477, 21482, 21483, 21485, 21486, 21494, 22082, 22084, 22087, 22107, 22141, 22142, 22181, 22192, and 22193) and the Protein Data Bank (PDB accession codes 6VU3, 6VYQ, 6VYR, 6VYS, 6VYT, 6VYU, 6VYW, 6VYX, 6VYY, 6VYZ, 6VZJ, 6VZ2, 6VZ3, 6VZ5, 6VZ7, 6XDQ, 6XDR, 6XGF, 6XII, 6XIJ, 6X6T, 6X7F, 6X7K, and 6X9Q). Materials are available from the authors on request.



Waksman Institute and Department of Chemistry and Chemical Biology, Rutgers University, Piscataway, NJ 08854, USA.
Waksman Institute and Department of Chemistry and Chemical Biology, Rutgers University, Piscataway, NJ 08854, USA.
Rutgers New Jersey CryoEM/CryoET Core Facility and Institute for Quantitative Biomedicine, Rutgers University, Piscataway, NJ 08854, USA.
Rutgers New Jersey CryoEM/CryoET Core Facility and Institute for Quantitative Biomedicine, Rutgers University, Piscataway, NJ 08854, USA.
Department of Biochemistry, University of California, Riverside, CA 92521, USA.
Life Sciences Institute, University of Michigan, Ann Arbor, MI,48109, USA.
Waksman Institute and Department of Chemistry and Chemical Biology, Rutgers University, Piscataway, NJ 08854, USA.

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These authors contributed equally to this work.
Corresponding author. Email: [email protected] (M.S.); [email protected] (R.H.E.)

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