T7 RNA Polymerase

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• Structure and Mechanism of T7 RNA polymerase

• Promoter Binding

• Elongation Complex Stability

• Interactive Structure Exploration

T7 RNA polymerase is an ideal model system for studying fundamental mechanisms in transcription. There are two broad classes of DNA-dependent RNA polymerases: 1) the multi-subunit polymerases, of which the bacterial RNA polymerase and eukaryotic Pol II are best known and 2) the single subunit RNA polymerases, of which T7 RNA polymerase and the mitochondrial (and chloroplast) RNA polymerases are best known. The single subunit enzymes are related to the large Pol I family of DNA and RNA polymerases. Although these two broad classes are evolutionarily distinct, the big picture mechanisms are a case of convergent evolution – similarities reflect the constraints of the complex challenge in evolving an enzyme that is initially very sequence-specific, but transitions to an enzyme that can transcribe any sequence.

T7 RNA polymerase is widely used to synthesize RNA in vitro, from a DNA template. The single subunit RNA polymerase from bacteriophage T7 was initially characterized in 1973, but with its cloning and over expression in 1984, it became a work horse for the in vitro synthesis of RNA of any length. The Uhlenbeck lab pioneered this application (and early on, described some limitations!). With the success of the SARS-CoV-2 vaccines, this use has been widely recognized and the Nobel Prize in Physiology or Medicine was awarded in 2023 to researchers who pioneered its use with modified bases. Coming from a bacteriophage with a 40 kb dsDNA genome, the enzyme has been used in vitro to generate RNA as long as 27 kb!