transposable element

Deep research

Generated by just research-trait; source: research/traits/genomics/transposable_element-deep-research-falcon.md

# Curation report: microbial transposable element

**Trait:** `traitmech:000092`  
**Category:** GENOMICS | **Term kind:** CLASS | **Mapping:** REVIEWED  
**Parent:** `traitmech:000089`

## 1. Scope summary

This trait should mean **genomic possession of at least one transposable element (TE)**: a DNA segment capable of changing genomic location through element-encoded or trans-supplied transposition machinery. In prokaryotes, an insertion sequence (IS) is the simplest autonomous form—typically a transposase ORF bounded by cognate ends—whereas larger or composite transposons may additionally carry “passenger” genes such as antimicrobial-resistance determinants. Nonautonomous elements belong in scope when recognizable as transposase-mobilizable TE derivatives. (hickman2016dnatranspositionat pages 2-3, siguier2014bacterialinsertionsequences pages 12-13)

The trait records **possession**, not necessarily current transposition activity. A defective or transcriptionally silent TE can therefore satisfy the trait, while an assay showing transposition rate is a related but different phenotype. Likewise, Tn-seq libraries made by experimentally delivering engineered Tn5/Mariner elements do not establish that the tested wild-type strain naturally possesses a TE. Modern Tn-seq constructs commonly place transposase outside the inserted segment to prevent remobilization. (fernandezgarcia2024essentialgenesdiscovery pages 2-4, fernandezgarcia2024essentialgenesdiscovery pages 1-2)

### Boundary cases

- **Include:** autonomous ISs; simple and composite transposons; replicative transposons; mobilizable nonautonomous TE derivatives; chromosomal or plasmid-borne elements.
- **Do not equate with:** plasmid possession, integron possession, prophage, integrative/conjugative elements, or horizontal gene transfer generally. These entities can carry or interact with TEs but have distinct replication/transfer machinery.
- **Do not require:** a resistance gene, terminal inverted repeats, target-site duplication, or a cut-and-paste mechanism. These are common but not universal. HUH-family elements use different chemistry, and some “peel-and-paste” systems do not produce target-site duplications. (hickman2016dnatranspositionat pages 5-6, tenjocastano2022transposonsandcrispr pages 2-3)
- **Assay caution:** a transposase annotation alone is suggestive, but fragmented assemblies and domesticated transposases can produce false-positive trait calls. Prefer a bounded element architecture, family assignment, or insertion evidence.

## 2. Current mechanistic model

The most defensible generic causal chain is:

**TE DNA containing cognate ends → transposase binding → end cleavage/excision or replicative strand transfer → target-DNA capture and integration → gap repair/target-site duplication where applicable → insertional mutation, altered neighboring-gene expression, or genome rearrangement → genomic plasticity.**

Transposases are site-specific endonucleases for their own element ends but are often less sequence-specific toward target DNA. In canonical DDE systems, acidic active-site residues coordinate divalent metal ions; exposed 3′-OH groups then attack target-DNA phosphodiester bonds. (hickman2016dnatranspositionat pages 3-5)

Mechanistic branching is essential. Cut-and-paste systems excise the donor copy; copy-in/replicative systems retain and duplicate it; copy-out–paste-in pathways pass through circular intermediates. IS200/IS605- and IS91-related HUH transposases instead use single-stranded intermediates and covalent 5′-phosphotyrosine linkages. (hickman2016dnatranspositionat pages 5-6, hickman2016dnatranspositionat pages 2-3)

For Tn3-family replicative transposition, transposase nicks both 3′ ends, the resulting 3′-OH groups attack staggered target strands, and repair of 5-bp gaps generates 5-bp direct target-site duplications in the cointegrate. This exact duplication length is family-specific and must not be generalized to all TEs. (nicolas2015thetn3familyof pages 13-15)

## 3. Candidate nodes grouped by type

### A. Trait and element-architecture nodes

- `traitmech:000092` — transposable element possession
- insertion sequence; simple transposon; composite transposon
- autonomous TE; nonautonomous TE
- transposon left end/right end
- terminal inverted repeat
- passenger gene/cargo DNA
- target-site duplication

These architecture nodes should remain **label-only** unless the project has verified ontology terms. ISfinder is the relevant specialist nomenclature resource; one review reported more than 4,000 classified IS sequences and about 30 recognized prokaryotic IS families at that time. (hickman2016dnatranspositionat pages 5-6)

### B. Genes, proteins, and complexes

- **transposase** — DDE/DD(E/D) or HUH catalytic class
- transpososome/synaptic complex
- **TnpR/resolvase** — family-scoped for cointegrate resolution
- H-NS, histone-like nucleoid-structuring protein
- TnsA, TnsB, TnsC, TnsD/TniQ and Cascade/Cas effector—only for Tn7/CAST branches
- IS-excision enhancer (IEE)—IS629-specific modifier

Recommended ontology-grounding candidates, subject to release-level verification, are **GO:0004803, transposase activity**, **GO:0006313, transposition, DNA-mediated**, and **GO:0003677, DNA binding**. Do not assign a generic transposase UniProt accession because transposases are element- and taxon-specific.

### C. Molecular intermediates and chemicals

- donor DNA and target DNA
- cleaved transposon-end 3′-OH

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