Mechanisms by which Bloom protein can disrupt recombination intermediates of Okazaki fragment maturation
| Autor: | Wensheng Wang, Robert A. Bambara, Jason E. Pike, Jeremy D. Bartos |
|---|---|
| Rok vydání: | 2006 |
| Předmět: |
DNA Repair
DNA repair Flap Endonucleases Biochemistry Substrate Specificity chemistry.chemical_compound Replication Protein A medicine Humans Bloom syndrome Molecular Biology Replication protein A Adenosine Triphosphatases Recombination Genetic biology Okazaki fragments RecQ Helicases DNA Helicases Helicase Cell Biology DNA medicine.disease Molecular biology Cell biology Kinetics chemistry biology.protein Nucleic Acid Conformation Homologous recombination Recombination |
| Zdroj: | The Journal of biological chemistry. 281(43) |
| ISSN: | 0021-9258 |
| Popis: | Bloom syndrome is a familial genetic disorder associated with sunlight sensitivity and a high predisposition to cancers. The mutated gene, Bloom protein (BLM), encodes a DNA helicase that functions in genome maintenance via roles in recombination repair and resolution of recombination structures. We designed substrates representing illegitimate recombination intermediates formed when a displaced DNA flap generated during maturation of Okazaki fragments escapes cleavage by flap endonuclease-1 and anneals to a complementary ectopic DNA site. Results show that displaced, replication protein A (RPA)-coated flaps could readily bind and ligate at the complementary site to initiate recombination. RPA also displayed a strand-annealing activity that hastens the rate of recombination intermediate formation. BLM helicase activity could directly disrupt annealing at the ectopic site and promote flap endonuclease-1 cleavage. Additionally, BLM has its own strand-annealing and strand-exchange activities. RPA inhibited the BLM strand-annealing activity, thereby promoting helicase activity and complex dissolution. BLM strand exchange could readily dissociate invading flaps, e.g. in a D-loop, if the exchange step did not involve annealing of RPA-coated strands. Use of ATP to activate the helicase function did not aid flap displacement by exchange, suggesting that this is a helicase-independent mechanism of complex dissociation. When RPA could bind, it displayed its own strand-exchange activity. We interpret these results to explain how BLM is well equipped to deal with alternative recombination intermediate structures. |
| Databáze: | OpenAIRE |
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