This paper has been prepared to commemorate the 70th anniversary of the Institute of Biophysics of the Czech Academy of Sciences (IBP CAS), which has a long-standing tradition in researching the biological effects of ionizing radiation (IR). Radiobiology has recently gained renewed importance due to several compelling factors. The demand for a better understanding of the biological effects of both low and high doses of various types of ionizing radiation, along with improved radiation protection, is increasing-particularly in the context of critical ongoing human activities such as medical diagnostics, radiotherapy, and the operation of nuclear power plants. This demand also extends to newly emerging scenarios, including the development of hadron and FLASH radiotherapy, as well as mixed radiation field exposures related to planned manned missions to Mars. Unfortunately, there is also an urgent need to address the heightened risk of nuclear materials and weapons misuse by terrorists or even rogue states. Additionally, nuclear energy is currently the only viable alternative that can provide efficient, sustainable, and ecological coverage for the dramatically increasing current and future energy demands. Understanding the risks of IR exposure necessitates exploring how different types of IR interact with living organisms at the most fundamental level of complexity, specifically at the level of molecules and their complexes. The rising interest in radiobiology is, therefore, also driven by new experimental opportunities that enable research at previously unimaginable levels of detail and complexity. In this manuscript, we will address the important questions in radiobiology, focusing specifically on the mechanisms of radiation-induced DNA damage and repair within the context of chromatin architecture. We will emphasize the differing effects of photon and high-LET particle radiation on chromatin and DNA. Both forms of IR are encountered on Earth but are particularly significant in space.

• Klíčová slova
• Biological effects of ionizing radiation, Chromatin architecture at micro- and nano-scale, DNA damage and repair, Densely ionizing (high-LET) particle radiation, Institute of biophysics of the Czech academy of sciences, Microscopy, Photon radiation, Radiobiological research, Single molecule localization microscopy (SMLM),
• Publikační typ
• časopisecké články MeSH
• přehledy MeSH

Complex functioning of the genome in the cell nucleus is controlled at different levels: (a) the DNA base sequence containing all relevant inherited information; (b) epigenetic pathways consisting of protein interactions and feedback loops; (c) the genome architecture and organization activating or suppressing genetic interactions between different parts of the genome. Most research so far has shed light on the puzzle pieces at these levels. This article, however, attempts an integrative approach to genome expression regulation incorporating these different layers. Under environmental stress or during cell development, differentiation towards specialized cell types, or to dysfunctional tumor, the cell nucleus seems to react as a whole through coordinated changes at all levels of control. This implies the need for a framework in which biological, chemical, and physical manifestations can serve as a basis for a coherent theory of gene self-organization. An international symposium held at the Biomedical Research and Study Center in Riga, Latvia, on 25 July 2022 addressed novel aspects of the abovementioned topic. The present article reviews the most recent results and conclusions of the state-of-the-art research in this multidisciplinary field of science, which were delivered and discussed by scholars at the Riga symposium.

• Klíčová slova
• database pattern analysis, dynamic genome organization, epigenetic interactions, fluorescence microscopy, gene activity oscillations, heterochromatin and self-organization, nucleotide k-mers, organizational and functional networks, topological genome analysis, transposon-effected regulation,
• MeSH
• buněčná diferenciace genetika   MeSH
• buněčné jádro * metabolismus   MeSH
• genom * MeSH
• Publikační typ
• kongresy MeSH
• přehledy MeSH

In cancer therapy, the application of (fractionated) harsh radiation treatment is state of the art for many types of tumors. However, ionizing radiation is a "double-edged sword"-it can kill the tumor but can also promote the selection of radioresistant tumor cell clones or even initiate carcinogenesis in the normal irradiated tissue. Individualized radiotherapy would reduce these risks and boost the treatment, but its development requires a deep understanding of DNA damage and repair processes and the corresponding control mechanisms. DNA double strand breaks (DSBs) and their repair play a critical role in the cellular response to radiation. In previous years, it has become apparent that, beyond genetic and epigenetic determinants, the structural aspects of damaged chromatin (i.e., not only of DSBs themselves but also of the whole damage-surrounding chromatin domains) form another layer of complex DSB regulation. In the present article, we summarize the application of super-resolution single molecule localization microscopy (SMLM) for investigations of these structural aspects with emphasis on the relationship between the nano-architecture of radiation-induced repair foci (IRIFs), represented here by γH2AX foci, and their chromatin environment. Using irradiated HeLa cell cultures as an example, we show repair-dependent rearrangements of damaged chromatin and analyze the architecture of γH2AX repair clusters according to topological similarities. Although HeLa cells are known to have highly aberrant genomes, the topological similarity of γH2AX was high, indicating a functional, presumptively genome type-independent relevance of structural aspects in DSB repair. Remarkably, nano-scaled chromatin rearrangements during repair depended both on the chromatin domain type and the treatment. Based on these results, we demonstrate how the nano-architecture and topology of IRIFs and chromatin can be determined, point to the methodological relevance of SMLM, and discuss the consequences of the observed phenomena for the DSB repair network regulation or, for instance, radiation treatment outcomes.

• Klíčová slova
• chromatin rearrangements after irradiation, ionizing radiation-induced foci (IRIF), nano-architecture, single molecule localization microscopy (SMLM), topology of DNA double strand breaks,
• MeSH
• chromatin genetika   ultrastruktura   MeSH
• dvouřetězcové zlomy DNA účinky záření   MeSH
• HeLa buňky MeSH
• ionizující záření MeSH
• lidé MeSH
• mikroskopie metody   MeSH
• nádorové buněčné linie MeSH
• nádory genetika   MeSH
• oprava DNA genetika   účinky záření   MeSH
• poškození DNA genetika   účinky záření   MeSH
• zobrazení jednotlivé molekuly metody   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• chromatin MeSH

In this work, we shed new light on the highly debated issue of chromatin fragmentation in cryopreserved cells. Moreover, for the first time, we describe replicating cell-specific DNA damage and higher-order chromatin alterations after freezing and thawing. We identified DNA structural changes associated with the freeze-thaw process and correlated them with the viability of frozen and thawed cells. We simultaneously evaluated DNA defects and the higher-order chromatin structure of frozen and thawed cells with and without cryoprotectant treatment. We found that in replicating (S phase) cells, DNA was preferentially damaged by replication fork collapse, potentially leading to DNA double strand breaks (DSBs), which represent an important source of both genome instability and defects in epigenome maintenance. This induction of DNA defects by the freeze-thaw process was not prevented by any cryoprotectant studied. Both in replicating and non-replicating cells, freezing and thawing altered the chromatin structure in a cryoprotectant-dependent manner. Interestingly, cells with condensed chromatin, which was strongly stimulated by dimethyl sulfoxide (DMSO) prior to freezing had the highest rate of survival after thawing. Our results will facilitate the design of compounds and procedures to decrease injury to cryopreserved cells.

• MeSH
• chromatin účinky léků   genetika   MeSH
• dimethylsulfoxid farmakologie   MeSH
• dvouřetězcové zlomy DNA účinky léků   MeSH
• fibroblasty MeSH
• kryoprezervace metody   MeSH
• kryoprotektivní látky farmakologie   MeSH
• kůže cytologie   MeSH
• lidé MeSH
• MFC-7 buňky MeSH
• S fáze účinky léků   MeSH
• viabilita buněk účinky léků   genetika   MeSH
• zmrazování škodlivé účinky   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Research Support, N.I.H., Extramural MeSH
• Research Support, U.S. Gov't, Non-P.H.S. MeSH
• Názvy látek
• chromatin MeSH
• dimethylsulfoxid MeSH
• kryoprotektivní látky MeSH