Tn5

Tn5 is a bacterial transposon, a small mobile genetic element that can move within and between DNA molecules. It belongs to the Tn5/Tn10 family of class II DNA transposons and is found in various Gram-negative bacteria, includingEscherichia coli and related species. The element is defined by inverted repeat sequences at its ends and a transposase gene (tnpA) that catalyzes its excision and insertion. Transposition generally proceeds via a cut-and-paste mechanism, producing short target-site duplications at the insertion sites and often not replicating the transposon during movement.

Structure and mechanism: Tn5 carries the genetic information needed for transposition, including the transposase and the terminal inverted repeats, sometimes referred to as mosaic ends. The transposase binds these ends, excises the element from its donor DNA, and integrates it into a target DNA site. The process can be influenced by host factors and cellular context.

Laboratory use: Tn5 has been widely exploited as a model transposon and as a practical tool in molecular biology. Insertion mutagenesis and tagging experiments employ Tn5 to generate insertional mutations in bacterial genomes or plasmids. A major modern application is in sequencing library preparation, where engineered Tn5 transposase is preloaded with sequencing adapters and used to simultaneously fragment DNA and tag it with adapters in a workflow known as tagmentation. This approach underpins rapid, scalable genome library construction and is central to several high-throughput sequencing methods.

Variations and safety: Engineered, hyperactive forms of Tn5 transposase have been developed to improve efficiency and reduce biases in libraries. As with all mobile genetic elements, use adheres to appropriate biosafety and regulatory guidelines, with attention to containment and ethical considerations in research.

See also: transposase, transposon, tagmentation, ATAC-seq.