Terminally-differentiated cells cease to proliferate and acquire specific sets of expressed genes and functions distinguishing them from less differentiated and cancer cells. Mature granulocytes show lobular structure of cell nuclei with highly condensed chromatin in which HP1 proteins are replaced by MNEI. These structural features of chromatin correspond to low level of gene expression and the loss of some important functions as DNA damage repair, shown in this work and, on the other hand, acquisition of a new specific function consisting in the release of chromatin extracellular traps in response to infection by pathogenic microbes. Granulocytic differentiation is incomplete in myeloid leukemia and is manifested by persistence of lower levels of HP1γ and HP1β isoforms. This immaturity is accompanied by acquisition of DDR capacity allowing to these incompletely differentiated multi-lobed neutrophils of AML patients to respond to induction of DSB by γ-irradiation. Immature granulocytes persist frequently in blood of treated AML patients in remission. These granulocytes contrary to mature ones do not release chromatin for NETs after activation with phorbol myristate-12 acetate-13 and do not exert the neutrophil function in immune defence. We suggest therefore the detection of HP1 expression in granulocytes of AML patients as a very sensitive indicator of their maturation and functionality after the treatment. Our results show that the changes in chromatin structure underlie a major transition in functioning of the genome in immature granulocytes. They show further that leukemia stem cells can differentiate ex vivo to mature granulocytes despite carrying the translocation BCR/ABL.

• MeSH
• akutní myeloidní leukemie genetika   metabolismus   patologie   MeSH
• buněčná diferenciace * MeSH
• chromatin genetika   MeSH
• chromozomální proteiny, nehistonové genetika   metabolismus   MeSH
• fluorescenční protilátková technika MeSH
• granulocyty metabolismus   patologie   MeSH
• hematopoetické kmenové buňky metabolismus   patologie   MeSH
• kultivované buňky MeSH
• kvantitativní polymerázová řetězová reakce MeSH
• lidé MeSH
• messenger RNA genetika   MeSH
• neutrofily patologie   MeSH
• polymerázová řetězová reakce s reverzní transkripcí MeSH
• poškození DNA * MeSH
• proliferace buněk MeSH
• tetradekanoylforbolacetát MeSH
• western blotting MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• srovnávací studie MeSH

In plants, different forms of programmed cell death (PCD) have been identified, but they only partially correspond to those described for animals, which is most probably due to structural differences between animal and plant cells. Here, the results show that in tobacco BY-2 cells, bleomycin (BLM), an inducer of double-strand breaks (DSBs), triggers a novel type of non-apoptotic PCD with paraptotic-like features. Analysis of numerous PCD markers revealed an extensive vacuolization, vacuolar rupture, and chromatin condensation, but no apoptotic DNA fragmentation, fragmentation of the nuclei, or sensitivity to caspase inhibitors. BLM-induced PCD was cell cycle regulated, occurring predominantly upon G(2)/M cell cycle checkpoint activation. In addition, this paraptotic-like PCD was at least partially inhibited by caffeine, a known inhibitor of DNA damage sensor kinases ATM and ATR. Interestingly, overexpression of one NtE2F transcriptional factor, whose homologues play a dual role in animal apoptosis and DNA repair, reduced PCD induction and modulated G(2)/M checkpoint activation in BY-2 cells. These observations provide a solid ground for further investigations into the paraptotic-like PCD in plants, which might represent an ancestral non-apoptotic form of PCD conserved among animals, protists, and plants.

• MeSH
• bleomycin farmakologie   MeSH
• buněčná smrt účinky léků   MeSH
• down regulace účinky léků   MeSH
• exprese genu účinky léků   MeSH
• fragmentace DNA účinky léků   MeSH
• kontrolní body buněčného cyklu účinky léků   MeSH
• protein-serin-threoninkinasy genetika   metabolismus   MeSH
• rostlinné proteiny genetika   metabolismus   MeSH
• tabák cytologie   účinky léků   genetika   metabolismus   MeSH
• transkripční faktory E2F genetika   metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

For the first time, DNA double-strand breaks (DSBs) were directly visualized in functionally and structurally different chromatin domains of human cells. The results show that genetically inactive condensed chromatin is much less susceptible to DSB induction by gamma-rays than expressed, decondensed domains. Higher sensitivity of open chromatin for DNA damage was accompanied by more efficient DSB repair. These findings follow from comparing DSB induction and repair in two 11 Mbp-long chromatin regions, one with clusters of highly expressed genes and the other, gene-poor, containing mainly genes having only low transcriptional activity. The same conclusions result from experiments with whole chromosome territories, differing in gene density and consequently in chromatin condensation. It follows from our further results that this lower sensitivity of DNA to the damage by ionizing radiation in heterochromatin is not caused by the simple chromatin condensation but very probably by the presence of a higher amount of proteins compared to genetically active and decondensed chromatin. In addition, our results show that some agents potentially used for cell killing in cancer therapy (TSA, hypotonic and hypertonic) influence cell survival of irradiated cells via changes in chromatin structure and efficiency of DSB repair in different ways.

• MeSH
• apoptóza účinky záření   MeSH
• buněčné jádro metabolismus   MeSH
• chromatin účinky záření   MeSH
• chromatinová imunoprecipitace MeSH
• DNA účinky záření   MeSH
• fibroblasty cytologie   metabolismus   účinky záření   MeSH
• fluorescenční protilátková technika MeSH
• G1 fáze fyziologie   účinky záření   MeSH
• histondeacetylasy metabolismus   MeSH
• hybridizace in situ fluorescenční MeSH
• inhibitory enzymů farmakologie   MeSH
• inhibitory histondeacetylas MeSH
• kůže cytologie   metabolismus   účinky záření   MeSH
• kyseliny hydroxamové farmakologie   MeSH
• lidé MeSH
• oprava DNA účinky záření   MeSH
• poškození DNA účinky záření   MeSH
• radioizotopy kobaltu MeSH
• regulace genové exprese účinky záření   MeSH
• S fáze fyziologie   účinky záření   MeSH
• záření gama MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• práce podpořená grantem MeSH