Note to users. If you're seeing this message, it means that your browser cannot find this page's style/presentation instructions -- or possibly that you are using a browser that does not support current Web standards. Find out more about why this message is appearing, and what you can do to make your experience of our site the best it can be.

Science 24 October 2008:
Vol. 322. no. 5901, pp. 553 - 557
DOI: 10.1126/science.1163433
Prev | Table of Contents | Next

Research Articles

The Structure of a Transcribing T7 RNA Polymerase in Transition from Initiation to Elongation

Kimberly J. Durniak,1 Scott Bailey,1,2* Thomas A. Steitz1,2,3{dagger}

Structural studies of the T7 bacteriophage DNA-dependent RNA polymerase (T7 RNAP) have shown that the conformation of the amino-terminal domain changes substantially between the initiation and elongation phases of transcription, but how this transition is achieved remains unclear. We report crystal structures of T7 RNAP bound to promoter DNA containing either a 7- or an 8-nucleotide (nt) RNA transcript that illuminate intermediate states along the transition pathway. The amino-terminal domain comprises the C-helix subdomain and the promoter binding domain (PBD), which consists of two segments separated by subdomain H. The structures of the intermediate complex reveal that the PBD and the bound promoter rotate by ~45° upon synthesis of an 8-nt RNA transcript. This allows the promoter contacts to be maintained while the active site is expanded to accommodate a growing heteroduplex. The C-helix subdomain moves modestly toward its elongation conformation, whereas subdomain H remains in its initiation- rather than its elongation-phase location, more than 70 angstroms away.

1 Department of Molecular Biophysics and Biochemistry, Yale University, 266 Whitney Avenue, New Haven, CT 06520–8114, USA.
2 Howard Hughes Medical Institute, Yale University, 266 Whitney Avenue, New Haven, CT 06520–8114, USA.
3 Department of Chemistry, Yale University, 266 Whitney Avenue, New Haven, CT 06520–8114, USA.

* Present address: Department of Biochemistry and Molecular Biology, Bloomberg School of Public Health, Johns Hopkins University, 615 North Wolfe Street, Baltimore, MD 21205, USA.

{dagger} To whom correspondence should be addressed. E-mail: thomas.steitz{at}yale.edu

Read the Full Text


THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
A Promoter Recognition Mechanism Common to Yeast Mitochondrial and Phage T7 RNA Polymerases.
D. Nayak, Q. Guo, and R. Sousa (2009)
J. Biol. Chem. 284, 13641-13647
   Abstract »    Full Text »    PDF »


To Advertise     Find Products

Science. ISSN 0036-8075 (print), 1095-9203 (online)