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Chromatin modifications and dynamics during repair of a double-strand chromosome break in budding yeast

A single double-strand break (DSB) triggers the ATR/ATM (Mec1/Tel1)-dependent DNA damage response in budding yeast. These kinases phosophorylate not only histone H2A (γ-H2AX) but also the C-terminal threonine of histone H2B (γ-H2B), both of which contribute to checkpoint responses and repair of the DSB. Despite both being phosphorylated by the same kinases, γ-H2AX kinetics are much more rapid than that of γ-H2B, but when H2A is mutated to prevent its phosphorylation, γ-H2B kinetics adopt the rapid kinetics seen for γ-H2AX. Both modifications are removed the PP4 phosphatase. γ-H2AX and γ-H2B spread over ≥ 50 kb on either side of the DSB but they are nearly absent in strongly transcribed regions. When transcription is turned off, γ-H2AX rises to a high level within 10 min, catalyzed by either Mec1 or Tel1, even 5 h after the break was induced and when Tel1 is reported no longer to be associated with the DSB. We show that if a DSB is created within 15 kb of one yeast centromere that γ-H2AX and γ-H2B spread to the pericentromeric regions of all other chromosomes, demonstrating that the kinases can act in trans to regions of DNA that are located in close proximity.

When a DSB is created in a locus that can be repaired by gene conversion, 5’ to 3’ resection leads to the loss of well-positioned nucleosomes adjacent to the DSB. When repair is complete, nucleosomes are re-established, but the pattern is distinct from that seen prior to the break or when the repaired cells are allowed to replicate. Chromatin re-establishment is dependent on the histone chaperones CAF-1 and Asf1.

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This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Haber, J.E., Lee, CS., Lee, K. et al. Chromatin modifications and dynamics during repair of a double-strand chromosome break in budding yeast. Epigenetics & Chromatin 6 (Suppl 1), O16 (2013).

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