- The T3 promoter is a highly specific DNA sequence recognized exclusively by T3 RNA polymerase, originating from bacteriophage T3. It enables precise and efficient initiation of transcription in in vitro systems and is commonly used for synthesizing RNA transcripts with high yield and fidelity.
- The T3 promoter sequence is short and well-defined, typically 5′-AATTAACCCTCACTAAAGGG-3′, and must be placed immediately upstream of the DNA sequence to be transcribed.
- Because T3 RNA polymerase only initiates at this specific sequence, the promoter offers tight control over transcription, eliminating background expression from host RNA polymerases in bacterial or cell-free systems.
- The T3 promoter is often included in plasmid vectors alongside T7 and SP6 promoters to allow flexibility in RNA synthesis, such as for generating strand-specific probes or synthesizing sense and antisense transcripts from the same DNA template.
- Its orthogonality makes it useful in multi-gene or multi-step experiments where transcriptional interference must be avoided.
- Though less commonly used than the T7 promoter, the T3 system remains a reliable and precise tool for applications requiring targeted RNA transcription, particularly in molecular cloning, in vitro translation, and diagnostic probe development.
