Averbeck, Nicole

Becker, G.

Durante, M.

Jakob, B.

Leifke, A. L.

Merk, B.

Müller, I.

Taucher-Scholz, G.

Voss, K.-O.

GSI Repository

Species conserved response at heterochromatic DNA damage ∗I. Mu¨ller1, B. Merk1, K.-O. Voss1, N. B. Averbeck1, B. Jakob1, A. L. Leifke1, G. Becker1, M.Durante1,2, and G. Taucher-Scholz1,31GSI Helmholtzzentrum fu¨r Schwerionenforschung GmbH, Darmstadt, Germany; 2TUD, Institut fu¨r Festko¨rperphysik,Darmstadt, Germany; 3TUD, Fachbereich Biologie, Darmstadt, GermanyDNA double strand break (DSB) repair comprises sev-eral steps; besides different repair proteins also chromatinmodifications are necessary and local as well as globalchromatin decondensation takes place. Furthermore, re-cent findings in Drosophila, mouse, and baker’s yeast showthat DSBs within repetitive regions relocate to less repeti-tive chromatin [1-3]. Thus, relocation of DSBs might be amechanism to prevent homology driven misrepair of repet-itive sequences. Here we provide evidence that in the fac-ultative heterochromatin of the human inactive X chromo-some (Xi) decondensation occurs at DNA damage (Fig. 1A and B) and DSBs are relocated to more open chromatin(Fig. 1 C, DSB marker 53BP1) [4]. Thus, DSB relocationis not limited to repetitive sequences but is a general pro-cess within repair of heterochromatic regions. Our resultsobtained in human cells indicate that decondensation at het-erochromatic DSBs and their relocation is conserved fromflies to mice and humans. In contrast to earlier findings [1-3], however, the DSB dependent chromatin modification ofH2AX phosphorylation (γH2AX) shows not only reloca-tion but additional H2AX phosphorylation takes place al-most in the entire Xi area (Fig. 1 C, γH2AX signal). Thisincreased γH2AX spreading is clearly LET (linear energytransfer) dependent as it is not seen upon carbon ion (notshown) but after calcium, titanium (not shown), or lead ion(Fig. 1 C) irradiation. The mechanism and functional rel-evance of this Xi wide γH2AX spreading will be analyzedin future studies.References[1] J. Torres-Rosell et al. Nat Cell Biol, 9 (2007) p. 923 ff[2] I. Chiolo et al. Cell, 144 (2011) p. 732 ff[3] B. Jakob et al. Nucleic Acids Res, 39 (2011) p. 6489 ff[4] I. Muller et al. Mutat Res, 756 (2013) p. 30 ff∗This work was part of HGS-HIRe and partially funded by the BMBFgrant 02NUK001A.Figure 1: (A) Chromatin decondensation in the Xi chro-mosome of human cells. Real time DNA decondensationwithin Xi territories (arrow) identified by Hoechst 33342DNA staining after irradiation with one gold ion at the GSImicroprobe. Selected images of indicated time points areshown. The appearance of a darker area within the Xi(magnification in white box) represents the Xi deconden-sation at the ion hit. (B) The depletion of DNA stainingintensities (i. e. occurrence of a darker area) over time atthe site of an ion hit is exemplarily shown for intensity pro-files along the line within the depicted Xi. (C) Relocationof heterochromatic DSBs is indicated by bending of 53BP1(DSB marker) tracks around Xi 1 h after low angle leadion (LET 13,500 keV/μm) irradiation (DNA signal: arrowindicates Xi; 53BP1 signal: arrow indicates bent 53BP1track). Phosphorylation of H2AX occurs all over the ionhit Xi (arrow in γH2AX signal). Scale bars: 5 μm.BIOPHYSICS-02 GSI SCIENTIFIC REPORT 2013204 doi:10.15120/GR-2014-1-BIOPHYSICS-02

Species conserved response at heterochromatic DNA damage

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Species conserved response at heterochromatic DNA damage

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