- T7 RNA polymerase is a highly specific and efficient RNA polymerase derived from bacteriophage T7, widely used in molecular biology for high-level expression of recombinant genes.
- Unlike E. coli RNA polymerase, T7 RNA polymerase recognizes only the T7 promoter, allowing for tight control and minimal interference from host transcriptional machinery.
- It transcribes genes at a significantly higher rate and with greater fidelity, making it an ideal tool for producing large amounts of RNA or protein in a short time.
- In bacterial expression systems—particularly in BL21(DE3) and its derivatives—the gene encoding T7 RNA polymerase is inserted into the chromosome under control of an inducible promoter, such as lacUV5.
- Upon IPTG induction, the polymerase is expressed and subsequently drives the transcription of a target gene placed downstream of a T7 promoter on a plasmid (e.g., in a pET vector).
- This two-tiered system offers tight regulation and high yield, making it one of the most powerful expression systems available for recombinant protein production. However, because of its strong activity, T7 RNA polymerase can sometimes lead to leaky expression, premature transcription, or the formation of toxic products or inclusion bodies.
- To mitigate these effects, researchers often use suppressor strains (like pLysS variants) that express T7 lysozyme, a natural inhibitor of the polymerase.
- Beyond bacterial expression, T7 RNA polymerase is also employed in in vitro transcription systems, synthetic biology, and vaccine development, highlighting its versatility and enduring importance in modern biotechnology.
