Target DNA structure plays a critical role in RAG transposition

Area of Science:

• Molecular Biology
• Genetics
• DNA Repair

Background:

• The RAG1/2 protein complex initiates antigen receptor gene rearrangements by recognizing recombination signal sequences (RSS).
• RAG recombinase can catalyze DNA transposition, integrating RSS-bounded DNA segments into target DNA, but this is rare in vivo despite being common in vitro.
• Non-B DNA structures, especially hairpins, are known to stimulate RAG transposition.

Purpose of the Study:

• To investigate the influence of hairpin tip sequence on RAG-mediated DNA transposition efficiency.
• To identify specific DNA sequences that can either stimulate or inhibit RAG transposition.

Main Methods:

• In vitro assays measuring RAG1/2-mediated transposition efficiency using various hairpin DNA targets.
• Analysis of the impact of specific nucleotide sequences at hairpin tips on transposition rates.

Main Results:

• The sequence of the four nucleotides at a hairpin tip significantly modulates transposition efficiency over a >100-fold range.
• Certain hairpin targets dramatically enhance transposition (up to 15% efficiency).
• One specific hairpin sequence acts as a potent inhibitor, blocking target capture and destabilizing complexes.

Conclusions:

• Hairpin tip sequence is a critical determinant of RAG transposition efficiency.
• Specific DNA structures can act as potent stimulators or inhibitors of RAG transposition in vitro.
• These findings suggest novel mechanisms for regulating RAG activity and transposition in vivo, potentially applicable to other transposases.