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Retrotransposition of a mouse L1 element.
1Department of Medical Genetics, Howard Hughes Medical Institute, University of Washington, Seattle 98195.
Summary
Long interspersed elements (LINEs), a type of repetitive DNA, are formally established as retrotransposons. Mouse L1 elements can transpose via RNA, even without their own reverse transcriptase, suggesting endogenous enzyme involvement.
Area of Science:
- Genetics
- Molecular Biology
- Genomics
Background:
- Long interspersed elements (LINEs) are a major class of mammalian repetitive DNA.
- L1 family elements are present at high copy numbers (10^4–10^5) per genome.
- Structural similarities suggest L1 elements may function as mobile genetic elements.
Purpose of the Study:
- To formally establish Long interspersed elements (L1) as retrotransposons.
- To investigate the mechanism of L1 element transposition.
- To determine if L1 elements require their own reverse transcriptase for retrotransposition.
Main Methods:
- Transfection of a tagged consensus mouse L1 element into baby hamster kidney cells.
- Deletion of the putative reverse transcriptase-encoding region of the L1 element.
- Observation of retrotransposition via an RNA intermediate.
Main Results:
- A tagged mouse L1 element demonstrated transposition via an RNA intermediate in transfected cells.
- This formally establishes L1 elements as retrotransposons.
- L1 elements lacking their own reverse transcriptase-encoding region still underwent retrotransposition.
Conclusions:
- L1 elements are confirmed retrotransposons.
- Retrotransposition of L1 elements can occur even when the element's own reverse transcriptase gene is deleted.
- Endogenous enzymes may supply the necessary reverse transcriptase activity for L1 element transposition.