Checkpoint adaptation was originally defined in yeast as the ability to divide despite the presence of damaged DNA. An important unanswered question is whether checkpoint adaptation also occurs in human cells. Here, we show that following the ionizing radiation-induced G(2) checkpoint, human osteosarcoma cells entered mitosis with gamma-H2AX foci, a marker for unrepaired DNA double-strand breaks. Exit from the G(2) checkpoint was accelerated by inhibiting the checkpoint kinase 1 (Chk1) and delayed by overexpressing wild-type Chk1 or depleting the Polo-like kinase 1 (Plk1). Chk1 and Plk1 controlled this process, at least partly, via independent signaling pathways. Our results suggest that human cells are able to exit the checkpoint arrest and divide before the damage has been fully repaired. Such cell division in the presence of damaged DNA may be detrimental for genetic stability and could potentially contribute to cancer development.

• MeSH
• fyziologická adaptace MeSH
• G2 fáze * účinky záření   MeSH
• lidé MeSH
• nádorové buněčné linie MeSH
• poškození DNA MeSH
• protein-serin-threoninkinasy * fyziologie   MeSH
• proteinkinasy * fyziologie   MeSH
• proteiny buněčného cyklu * fyziologie   MeSH
• protoonkogenní proteiny * fyziologie   MeSH
• Check Tag
• lidé MeSH

After fertilization, remodeling of the oocyte and sperm genome is essential for the successful initiation of mitotic activity in the fertilized oocyte and subsequent proliferative activity of the early embryo. Despite the fact that the molecular mechanisms of cell cycle control in early mammalian embryos are in principle comparable to those in somatic cells, there are differences resulting from the specific nature of the gene totipotency of the blastomeres of early cleavage embryos. In this review, we focus on the Chk1 kinase as a key transduction factor in monitoring the integrity of DNA molecules during early embryogenesis.

• MeSH
• checkpoint kinasa 1 * metabolismus   MeSH
• embryo savčí enzymologie   MeSH
• embryonální vývoj * genetika   MeSH
• poškození DNA * MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• přehledy MeSH

Léčbou volby v 1. linii metastatického renálního karcinomu (mRCC) je kombinace inhibitoru kontrolního bodu (CPI – checkpoint inhibitor) cíleného na dráhu PD-1 buď s dalším imunoonkologickým lékem, nebo s tyrosinkinázovým inhibitorem (TKI). Monoterapie TKI je možností léčby pro křehčí nemocné a pacienty s kontraindikací imunoterapie. Přibližně u 20–30 % pacientů léčených imunoterapií dochází k dlouhodobé kontrole onemocnění, která často přetrvává i po vysazení terapie. U ostatních pacientů se uplatňuje sekvenční léčba, jejíž strategie záleží na typu léčby v 1. linii. U pacientů s progresí po kombinované nebo sekvenční terapii CPI a TKI existuje několik léčebných možností: everolimus, kabozantinib, tivozanib, lenvatinib, opětovné podání CPI či inhibitor HIF-2 belzutifan, který je dosud v klinickém vývoji.

The treatment of choice in first-line therapy of metastatic renal cell carcinoma (mRCC) is the combination of a checkpoint inhibitor (CPI) targeting the PD-1 pathway with either another immuno-oncology drug or a tyrosine kinase inhibitor (TKI). TKI monotherapy is a treatment option for more fragile patients and patients with contra- indications to immunotherapy. Approximately 20–30% of patients treated with immunotherapy experience long- term disease control, which often persists even after discontinuation of therapy. In the remaining patients, sequential therapy is used, the strategy of which depends on the type of first-line treatment. For patients with progression after combination or sequential therapy with CPIs and TKIs, there are several treatment options: everolimus, cabozantinib, tivozanib, lenvatinib, CPI rechallenge or the HIF-2 inhibitor belzutifan, which is still in clinical development.

• MeSH
• inhibitory kontrolních bodů farmakologie   terapeutické užití   MeSH
• inhibitory tyrosinkinasy farmakologie   terapeutické užití   MeSH
• karcinom z renálních buněk * farmakoterapie   MeSH
• lidé MeSH
• protokoly protinádorové kombinované chemoterapie MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• práce podpořená grantem MeSH

When exposed to ionizing radiation (IR), eukaryotic cells activate checkpoint pathways to delay the progression of the cell cycle. Defects in the IR-induced S-phase checkpoint cause 'radioresistant DNA synthesis', a phenomenon that has been identified in cancer-prone patients suffering from ataxia-telangiectasia, a disease caused by mutations in the ATM gene. The Cdc25A phosphatase activates the cyclin-dependent kinase 2 (Cdk2) needed for DNA synthesis, but becomes degraded in response to DNA damage or stalled replication. Here we report a functional link between ATM, the checkpoint signalling kinase Chk2/Cds1 (Chk2) and Cdc25A, and implicate this mechanism in controlling the S-phase checkpoint. We show that IR-induced destruction of Cdc25A requires both ATM and the Chk2-mediated phosphorylation of Cdc25A on serine 123. An IR-induced loss of Cdc25A protein prevents dephosphorylation of Cdk2 and leads to a transient blockade of DNA replication. We also show that tumour-associated Chk2 alleles cannot bind or phosphorylate Cdc25A, and that cells expressing these Chk2 alleles, elevated Cdc25A or a Cdk2 mutant unable to undergo inhibitory phosphorylation (Cdk2AF) fail to inhibit DNA synthesis when irradiated. These results support Chk2 as a candidate tumour suppressor, and identify the ATM-Chk2-Cdc25A-Cdk2 pathway as a genomic integrity checkpoint that prevents radioresistant DNA synthesis.

• MeSH
• alely MeSH
• ATM protein MeSH
• buněčné linie MeSH
• buněčný cyklus * genetika   účinky záření   MeSH
• checkpoint kinasa 2 MeSH
• DNA vazebné proteiny MeSH
• fosfatasy cdc25 * fyziologie   účinky záření   MeSH
• fosforylace MeSH
• ionizující záření MeSH
• lidé MeSH
• myši MeSH
• nádorové supresorové proteiny MeSH
• protein-serin-threoninkinasy * fyziologie   MeSH
• proteinkinasy fyziologie   genetika   MeSH
• proteiny buněčného cyklu MeSH
• replikace DNA * účinky záření   MeSH
• S fáze účinky záření   MeSH
• serin metabolismus   MeSH
• signální transdukce MeSH
• tolerance záření MeSH
• transfekce MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• myši MeSH
• zvířata MeSH

To preserve genetic integrity, mammalian cells exposed to ionizing radiation activate the ATM kinase, which initiates a complex response-including the S-phase checkpoint pathways-to delay DNA replication. Defects in ATM or its substrates Nbs1 or Chk2 (ref. 3), the Nbs1-interacting Mre11 protein, or the Chk2-regulated Cdc25A-Cdk2 cascade all cause radio-resistant DNA synthesis (RDS). It is unknown, however, whether these proteins operate in a common signaling cascade. Here we show that experimental blockade of either the Nbs1-Mre11 function or the Chk2-triggered events leads to a partial RDS phenotype in human cells. In contrast, concomitant interference with Nbs1-Mre11 and the Chk2-Cdc25A-Cdk2 pathways entirely abolishes inhibition of DNA synthesis induced by ionizing radiation, resulting in complete RDS analogous to that caused by defective ATM. In addition, Cdk2-dependent loading of Cdc45 onto replication origins, a prerequisite for recruitment of DNA polymerase, was prevented upon irradiation of normal or Nbs1/Mre11-defective cells but not cells with defective ATM. We conclude that in response to ionizing radiation, phosphorylations of Nbs1 and Chk2 by ATM trigger two parallel branches of the DNA damage-dependent S-phase checkpoint that cooperate by inhibiting distinct steps of DNA replication.

• MeSH
• ATM protein MeSH
• buněčné linie MeSH
• checkpoint kinasa 2 MeSH
• cyklin-dependentní kinasa 2 MeSH
• cyklin-dependentní kinasy metabolismus   MeSH
• DNA vazebné proteiny MeSH
• fosfatasy cdc25 metabolismus   MeSH
• ionizující záření MeSH
• jaderné proteiny metabolismus   MeSH
• kinasy CDC2-CDC28 * MeSH
• lidé MeSH
• nádorové supresorové proteiny MeSH
• poškození DNA * MeSH
• protein-serin-threoninkinasy metabolismus   MeSH
• proteinkinasy metabolismus   MeSH
• proteiny buněčného cyklu MeSH
• S fáze * fyziologie   MeSH
• Check Tag
• lidé MeSH

When exposed to DNA-damaging insults such as ionizing radiation (IR) or ultraviolet light (UV), mammalian cells activate checkpoint pathways to halt cell cycle progression or induce cell death. Here we examined the ability of five commonly used anticancer drugs with different mechanisms of action to activate the Chk1/Chk2-Cdc25A-CDK2/cyclin E cell cycle checkpoint pathway, previously shown to be induced by IR or UV. Whereas exposure of human cells to topoisomerase inhibitors camptothecin, etoposide, or adriamycin resulted in rapid (within 1 h) activation of the pathway including degradation of the Cdc25A phosphatase and inhibition of cyclin E/CDK2 kinase activity, taxol failed to activate this checkpoint even after a prolonged treatment. Unexpectedly, although the alkylating agent cisplatin also induced degradation of Cdc25A (albeit delayed, after 8-12 h), cyclin E/CDK2 activity was elevated and DNA synthesis continued, a phenomena that correlated with increased E2F1 protein levels and consequently enhanced expression of cyclin E. These results reveal a differential impact of various classes of anticancer chemotherapeutics on the Cdc25A-degradation pathway, and indicate that the kinetics of checkpoint induction, and the relative balance of key components within the DNA damage response network may dictate whether the treated cells arrest their cell cycle progression.

• MeSH
• aktivace enzymů účinky léků   MeSH
• buněčný cyklus MeSH
• checkpoint kinasa 2 MeSH
• cisplatina farmakologie   MeSH
• cyklin E metabolismus   MeSH
• DNA metabolismus   MeSH
• doxorubicin farmakologie   MeSH
• etoposid farmakologie   MeSH
• fosfatasy cdc25 * metabolismus   MeSH
• fytogenní protinádorové látky farmakologie   MeSH
• inhibitory topoisomerasy I * MeSH
• inhibitory topoisomerasy II * MeSH
• ionizující záření MeSH
• kamptothecin farmakologie   MeSH
• kinetika MeSH
• lidé MeSH
• monoklonální protilátky metabolismus   MeSH
• nádorové buněčné linie MeSH
• osteosarkom MeSH
• paclitaxel farmakologie   MeSH
• poškození DNA účinky léků   účinky záření   MeSH
• protein-serin-threoninkinasy metabolismus   MeSH
• proteinkinasy metabolismus   MeSH
• protinádorová antibiotika farmakologie   MeSH
• průtoková cytometrie MeSH
• transformované buněčné linie MeSH
• ultrafialové záření MeSH
• Check Tag
• lidé MeSH

• Klíčová slova
• studie CaboPoint, kabozantinib,
• MeSH
• inhibitory kontrolních bodů farmakologie   terapeutické užití   MeSH
• inhibitory tyrosinkinasy * farmakologie   klasifikace   terapeutické užití   MeSH
• karcinom z renálních buněk * farmakoterapie   sekundární   MeSH
• lidé MeSH
• progrese nemoci MeSH
• prospektivní studie MeSH
• výsledek terapie MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• přehledy MeSH

• MeSH
• financování organizované MeSH
• genetická predispozice k nemoci genetika   MeSH
• genetické komponenty genetika   MeSH
• genetické poradenství metody   využití   MeSH
• lidé MeSH
• mutace genetika   MeSH
• nehodgkinský lymfom genetika   MeSH
• protein-serin-threoninkinasy genetika   MeSH
• Check Tag
• lidé MeSH

MRE11, RAD50 and NBS1 form a highly conserved protein complex (the MRE11 complex) that is involved in the detection, signalling and repair of DNA damage. We identify MDC1 (KIAA0170/NFBD1), a protein that contains a forkhead-associated (FHA) domain and two BRCA1 carboxy-terminal (BRCT) domains, as a binding partner for the MRE11 complex. We show that, in response to ionizing radiation, MDC1 is hyperphosphorylated in an ATM-dependent manner, and rapidly relocalizes to nuclear foci that also contain the MRE11 complex, phosphorylated histone H2AX and 53BP1. Downregulation of MDC1 expression by small interfering RNA yields a radio-resistant DNA synthesis (RDS) phenotype and prevents ionizing radiation-induced focus formation by the MRE11 complex. However, downregulation of MDC1 does not abolish the ionizing radiation-induced phosphorylation of NBS1, CHK2 and SMC1, or the degradation of CDC25A. Furthermore, we show that overexpression of the MDC1 FHA domain interferes with focus formation by MDC1 itself and by the MRE11 complex, and induces an RDS phenotype. These findings reveal that MDC1-mediated focus formation by the MRE11 complex at sites of DNA damage is crucial for the efficient activation of the intra-S-phase checkpoint.

• MeSH
• buněčné linie MeSH
• checkpoint kinasa 2 MeSH
• chromozomální proteiny, nehistonové metabolismus   MeSH
• DNA vazebné proteiny chemie   metabolismus   MeSH
• enzymy opravy DNA MeSH
• fosfatasy cdc25 MeSH
• fosforylace účinky záření   MeSH
• ionizující záření MeSH
• jaderné proteiny chemie   metabolismus   MeSH
• lidé MeSH
• myši MeSH
• nádorové buňky kultivované MeSH
• poškození DNA * MeSH
• protein-serin-threoninkinasy * MeSH
• proteinkinasy metabolismus   MeSH
• proteiny buněčného cyklu metabolismus   MeSH
• S fáze MeSH
• terciární struktura proteinů MeSH
• trans-aktivátory chemie   metabolismus   MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• myši MeSH
• zvířata MeSH

The Chk2 kinase is a tumor suppressor and key transducer of DNA-damage checkpoints. We show that the human Chk2 protein is relatively stable, nuclear, and responding to gamma-radiation throughout the cell cycle. Contrary to the retinoblastoma protein-regulated, labile Chk1 kinase restricted to S-G(2) phases, Chk2 remains activatable even in quiescent and differentiating cells. In human tissues, Chk2 is homogeneously expressed in renewing cell populations such as epidermis or intestine, heterogeneous in conditionally renewing tissues, and absent or cytoplasmic in static tissues such as muscle or brain. These data highlight striking differences between Chk2 and Chk1 and show unexpected correlation of Chk2 expression with tissue biology.

• MeSH
• aktivace enzymů MeSH
• buněčná diferenciace fyziologie   MeSH
• buněčné dělení fyziologie   MeSH
• buněčné linie MeSH
• buněčný cyklus fyziologie   MeSH
• checkpoint kinasa 2 MeSH
• fibroblasty cytologie   enzymologie   MeSH
• G1 fáze fyziologie   MeSH
• lidé MeSH
• monoklonální protilátky MeSH
• nádorové buňky kultivované MeSH
• osteosarkom enzymologie   patologie   MeSH
• poškození DNA * fyziologie   MeSH
• protein-serin-threoninkinasy * MeSH
• proteinkinasy fyziologie   imunologie   metabolismus   MeSH
• S fáze fyziologie   MeSH
• Check Tag
• lidé MeSH