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EMBO reports 5, 5, 497–502 (2004)
doi:10.1038/sj.embor.7400128
Published online: 8 April 2004
The absence of the yeast chromatin assembly factor Asf1 increases genomic instability and sister chromatid exchange
Félix Prado, Felipe Cortés-Ledesma & Andrés Aguilera
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Departamento de Genética, Facultad de Biología, Universidad de Sevilla, Avda. Reina Mercedes 6, 41012 Sevilla, Spain
To whom correspondence should be addressed
Andrés Aguilera Tel: +34 954557107; Fax: +34 954557104; E-mail: aguilo@us.es
Received 4 August 2003; Accepted 24 February 2004; Published online 8 April 2004.
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Abstract
Histone chaperone Asf1 participates in heterochromatin silencing, DNA repair and regulation of gene expression, and promotes the assembly of DNA into chromatin in vitro. To determine the influence of Asf1 on genetic stability, we have analysed the effect of asf1 on homologous recombination. In accordance with a defect in nucleosome assembly, asf1 leads to a loss of negative supercoiling in plasmids. Importantly, asf1 increases spontaneous recombination between inverted DNA sequences. This increase correlates with an accumulation of double-strand breaks (DSBs) as determined by immunodetection of phosphorylated histone H2A and fluorescent detection of Rad52–YFP foci during S and G2/M phases. In addition, asf1 shows high levels of sister chromatid exchange (SCE) and is proficient in DSB-induced SCE as determined by physical analysis. Our results suggest that defective chromatin assembly caused by asf1 leads to DSBs that can be repaired by SCE, affecting genetic stability.
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