Please use this identifier to cite or link to this item: doi:10.22028/D291-34461
Title: Focused Ion Microbeam Irradiation Induces Clustering of DNA Double-Strand Breaks in Heterochromatin Visualized by Nanoscale-Resolution Electron Microscopy
Author(s): Lorat, Yvonne
Reindl, Judith
Isermann, Anna
Rübe, Christian
Friedl, Anna A.
Rübe, Claudia E.
Language: English
Title: International Journal of Molecular Sciences
Volume: 22
Issue: 14
Publisher/Platform: MDPI
Year of Publication: 2021
Free key words: carbon ions
charged-particle radiotherapy
microbeam irradiation
DNA double-strand breaks (DSBs)
non-homologous end joining (NHEJ)
transmission electron microscopy (TEM)
DDC notations: 610 Medicine and health
Publikation type: Journal Article
Abstract: Background: Charged-particle radiotherapy is an emerging treatment modality for radioresistant tumors. The enhanced effectiveness of high-energy particles (such as heavy ions) has been related to the spatial clustering of DNA lesions due to highly localized energy deposition. Here, DNA damage patterns induced by single and multiple carbon ions were analyzed in the nuclear chromatin environment by different high-resolution microscopy approaches. Material and Methods: Using the heavy-ion microbeam SNAKE, fibroblast monolayers were irradiated with defined numbers of carbon ions (1/10/100 ions per pulse, ipp) focused to micrometer-sized stripes or spots. Radiation-induced lesions were visualized as DNA damage foci (γH2AX, 53BP1) by conventional fluorescence and stimulated emission depletion (STED) microscopy. At micro- and nanoscale level, DNA double-strand breaks (DSBs) were visualized within their chromatin context by labeling the Ku heterodimer. Single and clustered pKu70-labeled DSBs were quantified in euchromatic and heterochromatic regions at 0.1 h, 5 h and 24 h post-IR by transmission electron microscopy (TEM). Results: Increasing numbers of carbon ions per beam spot enhanced spatial clustering of DNA lesions and increased damage complexity with two or more DSBs in close proximity. This effect was detectable in euchromatin, but was much more pronounced in heterochromatin. Analyzing the dynamics of damage processing, our findings indicate that euchromatic DSBs were processed efficiently and repaired in a timely manner. In heterochromatin, by contrast, the number of clustered DSBs continuously increased further over the first hours following IR exposure, indicating the challenging task for the cell to process highly clustered DSBs appropriately. Conclusion: Increasing numbers of carbon ions applied to sub-nuclear chromatin regions enhanced the spatial clustering of DSBs and increased damage complexity, this being more pronounced in heterochromatic regions. Inefficient processing of clustered DSBs may explain the enhanced therapeutic efficacy of particle-based radiotherapy in cancer treatment.
DOI of the first publication: 10.3390/ijms22147638
Link to this record: urn:nbn:de:bsz:291--ds-344612
ISSN: 1422-0067
Date of registration: 3-Aug-2021
Description of the related object: Supplementary Materials
Related object:
Faculty: M - Medizinische Fakultät
Department: M - Radiologie
Professorship: M - Prof. Dr. Christian Rübe
Collections:SciDok - Der Wissenschaftsserver der Universität des Saarlandes

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