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Completion of LINE integration involves an open '4-way' branched DNA intermediate
Brijesh B Khadgi1, Aruna Govindaraju1, Shawn M Christensen1
1Department of Biology, University of Texas at Arlington, Arlington, TX 76019, USA.
Nucleic Acids Research
|August 9, 2019
Summary
Long Interspersed Elements (LINEs) integration involves a novel DNA junction intermediate. This structure is cleaved by the element protein, enabling second-strand DNA synthesis and completing the retrotransposition process.
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- Long Interspersed Elements (LINEs) are non-LTR retrotransposons that transpose via reverse transcription.
- The mechanism of LINE-mediated DNA integration, particularly the second-strand synthesis, is not fully understood.
Purpose of the Study:
- To investigate the in vitro mechanisms of second-strand DNA cleavage and synthesis during LINE integration.
- To elucidate the role of DNA structure in LINE integration.
Main Methods:
- Utilized purified components from a restriction-like endonuclease (RLE) bearing LINE.
- Performed in vitro assays to analyze DNA cleavage and synthesis.
- Characterized DNA structures involved in the integration intermediate.
Main Results:
- Identified a novel integration intermediate: an open '4-way' DNA junction.
- Demonstrated that the LINE element protein recognizes and cleaves this 4-way junction in a Holliday junction resolvase-like manner.
- Showed that cleavage of the 4-way junction generates a primer-template for second-strand DNA synthesis.
Conclusions:
- A new model for RLE LINE integration is proposed, highlighting the critical role of the 4-way DNA junction.
- The findings clarify a poorly understood step in the LINE retrotransposition lifecycle.