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In biotechnology applications, T7 RNA polymerase is commonly used to transcribe DNA that has been cloned into vectors that have two (different) phage promoters (e.g., T7 and T3, or T7 and SP6) in opposite orientation. RNA can be selectively synthesized from either strand of the insert DNA with the different polymerases.
(This polymerase originates from the T7 phage, a bacteriophage virus which infects E. coli bacterial cells and is capable of integrating its DNA into the host DNA, as well as overriding its cellular machinery to produce more copies of itself.) T7 RNA polymerase is responsible for beginning transcription at the T7 promoter of the transformed vector.
Usually, each member of this DNA library has a T7 RNA polymerase transcription site and a ribosomal binding site at the 5’ end. The T7 promoter region allows large-scale in vitro T7 transcription to transcribe the DNA library into an mRNA library, which provides templates for the in vitro translation reaction later.
The T7 promoter sequence is used extensively in molecular biology due to its extremely high affinity for T7 RNA polymerase and thus high level of expression. [3] [2] T7 has been used as a model in synthetic biology. Chan et al. (2005) "refactored" the genome of T7, replacing approximately 12 kbp of its genome with engineered DNA. [15]
[5] [6] The core RNA polymerase complex forms a "crab claw" or "clamp-jaw" structure with an internal channel running along the full length. [7] Eukaryotic and archaeal RNA polymerases have a similar core structure and work in a similar manner, although they have many extra subunits.
T7 RNA polymerase binds to the promoter region on the double strand. Since T7 RNA polymerase can only transcribe in the 3' to 5' direction [15] the sense DNA is transcribed and an anti-sense RNA is produced. This is repeated, and the polymerase continuously produces complementary RNA strands of this template which results in amplification.
T7 DNA polymerase is an enzyme used during the DNA replication of the T7 bacteriophage. During this process, the DNA polymerase “reads” existing DNA strands and creates two new strands that match the existing ones. The T7 DNA polymerase requires a host factor, E. coli thioredoxin, [1] in order to carry out its function
Although this polypeptide has the same function as the three nuclear DNA-directed RNA polymerases, it is more closely related to RNA polymerases of bacteriophage (including T7 RNA polymerase), mitochondrial polymerases of lower eukaryotes as well as chloroplastic RpoT polymerases. [6]