T7 DNA Polymerase Structure

Electron micrograph of the bacteriophage T7.

A virus is usually viewed as a problem, but T7 turned out to be useful, even valuable. In 1982, Brookhaven National Laboratory scientists, led by biologist William Studier, finished determining the DNA sequence of T7, a bacteriophage (bacteria-eating virus) that had the longest DNA sequence then known. When T7 invades a host cell, it makes proteins that turn off the host genes and turn on T7 genes. Researchers correlated the genetic map with T7's protein production, thereby acquiring a detailed understanding of how such viruses control their own replication. Studier and colleagues used this knowledge to develop a series of T7-based protein expression systems in which the gene of interest is silent until its expression is induced by a simple chemical trigger added to the culture. The protein products then are produced in abundance, even if the host cells eventually fail. In addition, the target genes can be engineered so that the proteins produced carry "affinity tags" enabling their rapid purification.

Scientific Impact: Widely used in molecular genetics and biotechnology, T7 protein expressions systems are noted for their reliability and adaptability. Even gene products that are difficult to express (e.g., toxic products) can be successfully produced using these systems.

Social Impact: The T7 system has become one of the most commercially successful, biologically based systems for producing large quantities of specific proteins. Even basic research using these systems sometimes has a practical impact, as in the case of recent work on a protein associated with Lyme disease that led to the development of improved vaccines.

Reference: Studier, F.W. and B.A. Moffatt, "Use of bacteriophage T7 RNA polymerase to direct selective high-level expression of cloned genes," J. Mol. Biol. 189: 113-130 (1986).

Studier, F.W., A.H. Rosenberg, J.J. Dunn and J.W. Dubendorff, "Use of T7 RNA polymerase to direct expression of cloned genes," Methods in Enzymology 185:60-89 (1990).

URL: http://bnlstb.bio.bnl.gov/biodocs/cellbio/Studier.htmlx

Technical Contact: Dr. Marvin Stodolsky, Life Sciences Division, Office of Biological and Environmental Research, 301-903-4742

Press Contact: Jeff Sherwood, DOE Office of Public Affairs, 202-586-5806

SC-Funding Office: Office of Biological and Environmental Research