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Related Concept Videos

LTR Retrotransposons03:08

LTR Retrotransposons

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LTR retrotransposons are class I transposable elements with long terminal repeats flanking an internal coding region. These elements are less abundant in mammals compared to other class I transposable elements. About 8 percent of human genomic DNA comprises LTR retrotransposons. Some of the common examples of LTR retrotransposons are Ty elements in yeast and Copia elements in Drosophila.
The internal coding region of LTR retrotransposons and their mechanism of transposition closely resembles a...
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Overview of Transposition and Recombination02:13

Overview of Transposition and Recombination

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Transposons make up a significant part of genomes of various organisms. Therefore, it is believed that transposition played a major evolutionary role in speciation by changing genome sizes and modifying gene expression patterns. For example, in bacteria, transposition can lead to conferring antibiotic resistance. Movement of transposable elements within the genetic pool of pathogenic bacteria can aid in transfer of antibiotic-resistant genetic elements. In eukaryotes, transposons can carry out...
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DNA-only Transposons02:57

DNA-only Transposons

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DNA-only transposons are called autonomous transposons since they code for the enzyme transposase that is required for the transposition mechanism. Insertion of transposons can alter gene functions in multiple ways. They can mutate the gene, alter gene expression by introducing a novel promoter or insulator sequence, introduce new splice sites, and change the mRNA transcripts produced, or remodel chromatin structure.
The donor site from where the transposon is excised is either degraded or...
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Homologous Recombination02:31

Homologous Recombination

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The basic reaction of homologous recombination (HR) involves two chromatids that contain DNA sequences sharing a significant stretch of identity. One of these sequences uses a strand from another as a template to synthesize DNA in an enzyme-catalyzed reaction. The final product is a novel amalgamation of the two substrates. To ensure an accurate recombination of sequences, HR is restricted to the S and G2 phases of the cell cycle. At these stages, the DNA has been replicated already and the...
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Non-LTR Retrotransposons03:18

Non-LTR Retrotransposons

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As the name suggests, non-LTR retrotransposons lack the long terminal repeats characteristic of the LTR retrotransposons. Additionally, both LTR and non-LTR retrotransposons use distinct mechanisms of mobilization. Non-LTR retrotransposons are further divided into two classes - Long interspersed nuclear elements (LINEs) and short interspersed nuclear elements (SINEs), both of which occur abundantly in most mammals, including humans. Some of the active non-LTR retrotransposons in humans are L1...
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Replication in Eukaryotes01:29

Replication in Eukaryotes

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In eukaryotic cells, DNA replication is highly conserved and tightly regulated. Multiple linear chromosomes must be duplicated with high fidelity before cell division, so there are many proteins that fulfill specialized roles in the replication process. Replication occurs in three phases: initiation, elongation, and termination, and ends with two complete sets of chromosomes in the nucleus.
Many Proteins Orchestrate Replication at the Origin
Eukaryotic replication follows many of the same...
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Related Experiment Video

Updated: Jul 23, 2025

Determination of the Optimal Chromosomal Locations for a DNA Element in Escherichia coli Using a Novel Transposon-mediated Approach
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Determination of the Optimal Chromosomal Locations for a DNA Element in Escherichia coli Using a Novel Transposon-mediated Approach

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Retrotransposons hijack alt-EJ for DNA replication and eccDNA biogenesis.

Fu Yang1, Weijia Su1, Oliver W Chung1

  • 1Department of Pharmacology and Cancer Biology, Duke University School of Medicine, Durham, NC, USA.

Nature
|July 12, 2023
PubMed
Summary
This summary is machine-generated.

Retrotransposons hijack the alternative end-joining (alt-EJ) DNA repair pathway to generate their second-strand DNA. This process is crucial for retrotransposon replication, eccDNA production, and new genomic insertions.

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Preparation of the Mgm101 Recombination Protein by MBP-based Tagging Strategy
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Last Updated: Jul 23, 2025

Determination of the Optimal Chromosomal Locations for a DNA Element in Escherichia coli Using a Novel Transposon-mediated Approach
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Quantitation and Analysis of the Formation of HO-Endonuclease Stimulated Chromosomal Translocations by Single-Strand Annealing in Saccharomyces cerevisiae
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Area of Science:

  • Genomics
  • Molecular Biology
  • DNA Repair

Background:

  • Retrotransposons are abundant in animal genomes and can impact host biology upon activation.
  • While retrotransposons synthesize first-strand DNA using reverse transcriptase, the mechanism for second-strand DNA synthesis remains unclear.
  • Uncontrolled retrotransposon activation is linked to disease and aging.

Purpose of the Study:

  • To elucidate the mechanism of second-strand DNA synthesis in retrotransposon replication.
  • To investigate the role of host DNA repair pathways in retrotransposon propagation.
  • To understand how retrotransposons generate extrachromosomal circular DNA (eccDNA).

Main Methods:

  • Utilized Nanopore sequencing to analyze retrotransposon DNA.
  • Employed genetic screens to identify host factors involved in retrotransposon replication.
  • Focused on extrachromosomal circular DNA (eccDNA) production as a key readout.

Main Results:

  • Identified that retrotransposons hijack the alternative end-joining (alt-EJ) DNA repair pathway for second-strand DNA synthesis.
  • Found that 90% of replicated retrotransposon DNA forms eccDNA, while 10% leads to new insertions.
  • Demonstrated that alt-EJ is essential for eccDNA production and subsequent retrotransposon insertions.

Conclusions:

  • Retrotransposons utilize the host's alt-EJ pathway for circularization and second-strand DNA synthesis.
  • The alt-EJ pathway is critical for the propagation of parasitic genomic retroelements.
  • This study reveals a conserved function of alt-EJ and offers insights into controlling the retrotransposon life cycle.