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Updated: Aug 8, 2026
14:23
Recombineering Homologous Recombination Constructs in Drosophila
Published on: July 13, 2013
In vitro V(D)J recombination: signal joint formation
P Cortes1, F Weis-Garcia, Z Misulovin
1Laboratory of Molecular Immunology, Howard Hughes Medical Institute, Rockefeller University, New York, NY 10021, USA.
Summary
Recombination activating proteins RAG1 and RAG2 alone cannot form signal joints. However, with nuclear extracts, they can create precise signal joints in a cell-free system, dependent on Ku antigen.
Area of Science:
- Molecular Biology
- Immunology
- Genetics
Background:
- V(D)J recombination is crucial for generating diverse antigen receptors in adaptive immunity.
- The initial step involves RAG1 and RAG2 proteins cleaving DNA at recombination signal sequences (RSS).
- Proper rejoining of cleaved DNA ends is essential for functional receptors and genomic stability.
Purpose of the Study:
- To investigate the requirements for signal joint formation in a cell-free system.
- To determine if RAG1 and RAG2 alone are sufficient for signal joint formation.
- To characterize the factors necessary for efficient and accurate signal joint resolution.
Main Methods:
- Utilized deletion and inversion substrates in an in vitro cell-free system.
- Assessed signal joint formation with RAG1 and RAG2 alone and in combination with nuclear extracts.
- Analyzed the reaction for Ku antigen dependence.
Main Results:
- RAG1 and RAG2 proteins alone, or together, did not generate signal joints.
- The addition of nuclear extracts to RAG1 and RAG2 enabled the recombination of an extrachromosomal substrate.
- Precise signal joints were formed in vitro, and the reaction was dependent on Ku antigen.
- The in vitro system mimicked authentic V(D)J recombination processes.
Conclusions:
- RAG1 and RAG2 require additional factors present in nuclear extracts for signal joint formation.
- Ku antigen is essential for the in vitro signal joint formation mediated by RAG1/RAG2 and nuclear extracts.
- This cell-free system provides a valuable tool for studying V(D)J recombination mechanisms.
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