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V(D)J recombination: a functional definition of the joining signals
J E Hesse1, M R Lieber, K Mizuuchi
1Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, Maryland 20892.
Genes & Development
|July 1, 1989
Summary
The heptamer sequence is crucial for V(D)J recombination, with specific bases near the crossover site being most important. Minor variations in the nonamer sequence do not significantly impact recombination efficiency.
Area of Science:
- Immunology
- Molecular Biology
- Genetics
Background:
- V(D)J recombination assembles immunoglobulin and T-cell receptor genes from V, D, and J segments.
- This process relies on two conserved DNA joining signals: the heptamer and nonamer sequences.
Purpose of the Study:
- To investigate the role of specific sequences within the heptamer and nonamer joining signals in V(D)J recombination.
- To determine the relative importance of the heptamer and nonamer sequences and their components.
Main Methods:
- Utilized plasmid substrates with mutations in heptamer-spacer-nonamer sequences.
- Tested recombination efficiency in a pre-B-cell line active in V(D)J recombination.
Main Results:
- Mutated signal variants did not recombine more efficiently than consensus sequences.
- The heptamer sequence, particularly bases near the crossover site, is critical for recombination.
- The nonamer sequence is less rigidly defined, and the five consecutive As are not essential.
Conclusions:
- The heptamer sequence plays a more significant role than the nonamer in V(D)J recombination.
- Spacer length intolerance (±1 bp) is common to both signal types.
- Homology between signals does not appear to play a role in recombination, suggesting they function as protein binding sites.