Visualization of human Bloom's syndrome helicase molecules bound to homologous recombination intermediates.
FASEB J
; 27(12): 4954-64, 2013 Dec.
Article
em En
| MEDLINE
| ID: mdl-24005907
ABSTRACT
Homologous recombination (HR) is a key process in the repair of double-stranded DNA breaks (DSBs) that can initiate cancer or cell death. Human Bloom's syndrome RecQ-family DNA helicase (BLM) exerts complex activities to promote DSB repair while avoiding illegitimate HR. The oligomeric assembly state of BLM has been a key unresolved aspect of its activities. In this study we assessed the structure and oligomeric state of BLM, in the absence and presence of key HR-intermediate DNA structures, by using single-molecule visualization (electron microscopic and atomic force microscopic single-particle analysis) and solution biophysical (dynamic light scattering, kinetic and equilibrium binding) techniques. Besides full-length BLM, we used a previously characterized truncated construct (BLM(642-1290)) as a monomeric control. Contrary to previous models proposing a ring-forming oligomer, we found the majority of BLM molecules to be monomeric in all examined conditions. However, BLM showed a tendency to form dimers when bound to branched HR intermediates. Our results suggest that HR activities requiring single-stranded DNA translocation are performed by monomeric BLM, while complex DNA structures encountered and dissolved by BLM in later stages of HR induce partial oligomerization of the helicase.
Palavras-chave
Texto completo:
1
Base de dados:
MEDLINE
Assunto principal:
DNA de Cadeia Simples
/
RecQ Helicases
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Recombinação Homóloga
Limite:
Humans
Idioma:
En
Ano de publicação:
2013
Tipo de documento:
Article