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RAG transposase can capture and commit to target DNA before or after donor cleavage
M B Neiditch1, G S Lee, M A Landree
1Department of Immunology, Baylor College of Medicine, Houston, Texas 77030, USA.
Molecular and Cellular Biology
|June 8, 2001
Summary
The V(D)J recombinase, acting as a transposase, can bind target DNA early in transposition. This target commitment, dependent on the DDE motif, may favor transposition near existing V(D)J recombination sites.
Area of Science:
- Genetics
- Molecular Biology
- Genomic Instability
Background:
- The V(D)J recombinase exhibits transposase activity in vitro.
- This suggests a potential role in genomic instability.
- Understanding its regulation is crucial.
Purpose of the Study:
- Investigate target commitment in V(D)J recombinase transposition.
- Elucidate mechanisms regulating RAG transposase-target DNA interactions.
- Determine the rate-limiting step in transposition.
Main Methods:
- Studied target commitment phenomenon.
- Analyzed functional association between RAG transposase and target DNA.
- Assessed complex formation before and after donor cleavage.
- Investigated the role of the DDE motif and active-site residues.
Main Results:
- V(D)J recombinase forms productive complexes with target DNA both before and after cleavage.
- Transposition rate is limited after target capture.
- Stable target capture requires active-site metal binding residues (DDE motif).
- RAG-1 active-site amino acids are critical for target capture.
Conclusions:
- RAG transposase commits to target DNA prior to cleavage.
- This may lead to localized transposition, favoring immunoglobulin and T-cell receptor loci.
- Localized transposition could bias recombination towards safer genomic regions.
- This preference may have influenced antigen receptor locus evolution.