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Joined 2026-09-21 Message
Incoming links: Tn5
DNA transposition 2026-11-05
DNA transposition is the relocation or insertional copying of a defined DNA segment through the action of transposition machinery. The DNA transposon is the mobile sequence; DNA transposition is the process. In a DNA-mediated system, transposase recognizes the relevant ends and coordinates their chemical processing and transfer into target DNA. Individual systems differ in whether a donor copy is removed or retained.[ref]
A unified classification system for eukaryotic transposable elements by Thomas Wicker and others. DNA-intermediate classification and mechanistically distinct classII groups
The Tn5 system reveals how two ends can be coordinated. A 2000 structure of Tn5 transposase bound to transposon-end DNA showed two protein subunits organizing the ends into catalytic positions. Each end contacted both subunits, and the structural model explained how end recognition and cleavage could involve different subunits.[ref]
For a bookkeeping example, label a mobile segment
X. An excision assay can establish that the donor junction changed from A-X-B to a repaired arrangement lacking X. That observation alone does not locate X elsewhere. A new recipient junction containing X establishes an additional event. Measuring DNA transposition therefore requires distinguishing end recognition, cleavage, target insertion and subsequent DNA repair, rather than treating any one signal as proof of every step. Tn5 2026-11-05
Tn5 is a bacterial DNA transposon used as a model for how mobile DNA ends are recognized, processed and inserted into another DNA molecule. The element is a DNA sequence; Tn5 transposase is the protein that supplies its catalytic machinery. The assembled enzyme–DNA complex is a transpososome.
A 2000 structure determined Tn5 transposase bound to transposon-end DNA at resolution. Two protein subunits contacted each end and positioned the ends in the active sites. The geometry explained how recognition by one subunit and cleavage by the other could coordinate the reaction.[ref]
Three-dimensional structure of the Tn5 synaptic complex transposition intermediate by D. R. Davies and others. Abstract, DNA-end complex, dimeric arrangement and catalytic geometry
This machinery became useful beyond studying a naturally mobile element. The 2013 ATAC-seq study used transposition to introduce sequencing adaptors into native chromatin, generating fragments informative about chromatin accessibility and molecular organization.[ref]
Transposition of native chromatin for fast and sensitive epigenomic profiling of open chromatin, DNA-binding proteins and nucleosome position by Jason D. Buenrostro and others. Abstract, transposition into native chromatin and accessible-region profiling
The distinction between element and enzyme clarifies the tool. A DNA fragment processed by a prepared Tn5 transposase complex need not itself contain the gene encoding the enzyme. Observing a tagged fragment therefore establishes an enzyme-mediated event, rather than showing that every product has acquired autonomous transposition machinery. The sequence, catalyst and experimental readout describe different parts of the system.