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Updated: Sep 24, 2025
06:24
Real-time Observation of the DNA Strand Exchange Reaction Mediated by Rad51
Published on: February 13, 2019
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Divergent binding mode for a protozoan BRC repeat to RAD51
Teodors Pantelejevs1, Marko Hyvönen1
1Department of Biochemistry, University of Cambridge, Cambridge CB2 1GA, U.K.
The Biochemical Journal
|May 3, 2022
Summary
Leishmania infantum BRCA2
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- The interaction between BRCA2 (Breast cancer gene 2) and RAD51 is crucial for DNA double-strand break repair via homologous recombination in eukaryotes.
- Human BRCA2 utilizes eight BRC repeats with two motifs (FxxA and LFDE) for RAD51 binding, but BRC repeat interactions in protozoans remain largely uncharacterized.
- Protozoan BRCA2 proteins exhibit a variable number of BRC repeats, suggesting potential evolutionary divergence in their interaction mechanisms.
Purpose of the Study:
- To investigate the detailed interactions of the two BRC repeats in Leishmania infantum BRCA2 (LiBRC1 and LiBRC2) with Leishmania infantum RAD51 (LiRAD51).
- To elucidate the structural basis of high-affinity binding between LiBRC1 and LiRAD51.
- To explore the evolutionary implications of BRC repeat interactions in DNA repair pathways.
Main Methods:
- Biochemical assays to study the interaction between Leishmania infantum BRCA2 BRC repeats and Leishmania infantum RAD51.
- X-ray crystallography to determine the structure of the LiBRC1-LiRAD51 complex.
- Truncation mutagenesis of the LiBRC1 repeat to identify key binding determinants.
Main Results:
- LiBRC1 was identified as a high-affinity RAD51-binding repeat.
- The crystal structure of the LiBRC1-LiRAD51 complex revealed specific interaction interfaces.
- High-affinity binding of LiBRC1 to LiRAD51 was retained even without an LFDE-like motif, indicating compensatory structural features.
Conclusions:
- Leishmania infantum BRCA2 BRC repeats interact with RAD51, with LiBRC1 being a high-affinity binder.
- The interaction mechanism of LiBRC1 with LiRAD51 differs from human BRCA2, lacking a canonical LFDE motif but maintaining high affinity through compensatory structures.
- These findings suggest a divergent evolutionary path for BRC repeats, originating from an FxxA-binding ancestor and evolving additional contacts for fine-tuning RAD51 interactions.
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