Checkpoint inhibition of origin firing prevents inappropriate replication in G2/M phase.
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ABSTRACT:
PROVIDER: PRJNA686785 | ENA |
REPOSITORIES: ENA
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Project description:Across eukaryotes, checkpoints maintain the order of cell cycle events in the face of DNA damage or incomplete replication. Although a wide array of DNA lesions activates the checkpoint kinases, whether and how this response differs in different phases of the cell cycle remains poorly understood. The S-phase checkpoint for example results in the slowing of replication, which in the budding yeast Saccharomyces cerevisiae is caused by Rad53 kinase-dependent inhibition of the initiation factors Sld3 and Dbf4. Despite this, we show here that Rad53 phosphorylates both of these substrates throughout the cell cycle at the same sites as in S-phase, suggesting roles for this pathway beyond S-phase. Indeed we show that Rad53-dependent inhibition of Sld3 and Dbf4 limits re-replication in G2/M phase, preventing inappropriate gene amplification events. In addition we show that inhibition of Sld3 and Dbf4 after DNA damage in G1 phase prevents premature replication initiation at all origins at the G1/S transition. This study redefines the scope and specificity of the ‘S-phase checkpoint’ with implications for understanding the roles of this checkpoint in the majority of cancers that lack proper cell cycle controls.
2021-01-14 | GSE163571 | GEO
Project description:Across eukaryotes, checkpoints maintain the order of cell cycle events in the face of DNA damage or incomplete replication. Although a wide array of DNA lesions activates the checkpoint kinases, whether and how this response differs in different phases of the cell cycle remains poorly understood. The S-phase checkpoint for example results in the slowing of replication, which in the budding yeast Saccharomyces cerevisiae is caused by Rad53 kinase-dependent inhibition of the initiation factors Sld3 and Dbf4. Despite this, we show here that Rad53 phosphorylates both of these substrates throughout the cell cycle at the same sites as in S-phase, suggesting roles for this pathway beyond S-phase. Indeed we show that Rad53-dependent inhibition of Sld3 and Dbf4 limits re-replication in G2/M phase, preventing inappropriate gene amplification events. In addition we show that inhibition of Sld3 and Dbf4 after DNA damage in G1 phase prevents premature replication initiation at all origins at the G1/S transition. This study redefines the scope and specificity of the ‘S-phase checkpoint’ with implications for understanding the roles of this checkpoint in the majority of cancers that lack proper cell cycle controls.
2021-01-14 | GSE159122 | GEO
Project description:Checkpoint inhibition of origin firing prevents inappropriate replication outside of S-phase
| PRJNA667726 | ENA
Project description:Hypoxia promotes an aggressive tumor phenotype with increased genomic instability, partially due to downregulation of DNA repair pathways. However, in addition to DNA repair, genome stability is also controlled by cell cycle checkpoints. An important issue is therefore whether hypoxia also can alter the DNA damage cell cycle checkpoints. Here, we show that hypoxia (24h 0.2% O2) alters the expression of several G2 checkpoint regulators, as examined by microarray gene expression analysis and immunoblotting of U2OS cells. While some of the changes reflected hypoxia-induced inhibition of cell cycle progression, flow cytometric bar-coding analysis of individual cells showed that the levels of several G2 checkpoint regulators were reduced in G2 phase cells after hypoxic exposure, in particular cyclin B1. These effects were accompanied by decreased Cyclin dependent kinase (CDK) activity in G2 phase cells after hypoxia. Furthermore, cells pre-exposed to hypoxia showed a longer G2 checkpoint arrest upon treatment with ionizing radiation. Similar results were found following other hypoxic conditions (~0.03 % O2 20h and 0.2% O2 72h). These results demonstrate that the DNA damage G2 checkpoint can be altered as a consequence of hypoxia, and we propose that such alterations may influence the genome stability of hypoxic tumors. We measured gene expression changes in U2OS cells after treatment with 0.2% hypoxia for 24 hours. The data were used in the exploration of hyopxia induced alterations in the G2 checkpoint.
2016-01-04 | E-GEOD-70530 | biostudies-arrayexpress
Project description:Mrc1 is a conserved checkpoint mediator protein that transduces replication-stress signal to downstream effector kinase. Loss of mrc1 checkpoint activity results in aberrant activation of late/dormant origins in the presence of hydroxyurea. Mrc1 was also suggested to regulate orders of early-origin firing in a checkpoint-independent manner, but its mechanism was unknown. Here we identify HBS (Hsk1 Bypass Segment) on Mrc1. ∆HBS does not suppress late/dormant origin firing in the presence of hydroxyurea but causes precocious and enhanced activation of weak early-firing origins during normal S-phase progression, and bypasses the requirement of Hsk1 for growth. This may be caused by disruption of intramolecular binding between HBS and NTHBS (N-terminal-Target-of-HBS). Hsk1 binds to Mrc1 through HBS and phosphorylates a segment adjacent to NTHBS, disrupting intramolecular interaction. We propose that Mrc1 exerts “brake” on initiation (through intra-molecular interaction) and this brake can be released (upon loss of intra-molecular interaction) by either Hsk1-mediated phosphorylation of Mrc1 or deletion of HBS (or phosphomimic mutation) which can bypass the function of Hsk1 for growth. The “brake” mechanism may explain the checkpoint-independent regulation of early origin firing in fission yeast.
2017-01-06 | GSE93178 | GEO
Project description: Not available
| S-EPMC7806266 | biostudies-literature
Project description:Hypoxia promotes an aggressive tumor phenotype with increased genomic instability, partially due to downregulation of DNA repair pathways. However, in addition to DNA repair, genome stability is also controlled by cell cycle checkpoints. An important issue is therefore whether hypoxia also can alter the DNA damage cell cycle checkpoints. Here, we show that hypoxia (24h 0.2% O2) alters the expression of several G2 checkpoint regulators, as examined by microarray gene expression analysis and immunoblotting of U2OS cells. While some of the changes reflected hypoxia-induced inhibition of cell cycle progression, flow cytometric bar-coding analysis of individual cells showed that the levels of several G2 checkpoint regulators were reduced in G2 phase cells after hypoxic exposure, in particular cyclin B1. These effects were accompanied by decreased Cyclin dependent kinase (CDK) activity in G2 phase cells after hypoxia. Furthermore, cells pre-exposed to hypoxia showed a longer G2 checkpoint arrest upon treatment with ionizing radiation. Similar results were found following other hypoxic conditions (~0.03 % O2 20h and 0.2% O2 72h). These results demonstrate that the DNA damage G2 checkpoint can be altered as a consequence of hypoxia, and we propose that such alterations may influence the genome stability of hypoxic tumors.
2016-01-04 | GSE70530 | GEO
Project description: Not available
| S-EPMC6824463 | biostudies-literature
Project description:PBRM1 is a subunit of the PBAF (SWI/SNF) chromatin remodelling complex that is mutated in approximately 40% of clear cell renal cell carcinomas (ccRCC). PBRM1 loss has been implicated in the response to immune checkpoint inhibitor (ICI) therapy in ccRCC. However, it is unclear how PBRM1 influences this. DNA damage-induced inflammatory signalling is an important factor determining ICI therapy response. This response is kept in check by the G2/M checkpoint, which prevents progression through mitosis with unrepaired damage. Here, we show that PBRM1 is required for p53-dependent maintenance of the G2/M checkpoint. In its absence, p53-dependent transcriptional upregulation of p21 is delayed, leading to defective repression of DREAM complex targets and premature entry into mitosis. Consequently, DNA damage induced inflammatory signalling pathways are activated by cytosolic DNA. Notably, p53 is infrequently mutated in ccRCC, so PBRM1 mutational status is critical to G2/M checkpoint maintenance following DNA damage in this cancer. These findings have implications for ICI therapy responses in ccRCC.
2022-10-13 | PXD028336 | Pride
Project description:The chromatin-based rules governing the selection and activation of replication origins remain to be elucidated. It is believed that DNA replication initiates from open chromatin domains, thus replication origins residing in regulatory elements that are located at open and active chromatin. However, we report here that lysine specific demethylase 1 (LSD1), which biochemically catalyzes H3K4me1/2 demethylation to favor chromatin condensation, interacts with the DNA replication machinery. We found that LSD1 level peaks in early S phase. We demonstrated that LSD1 promotes DNA replication by facilitating origin firing in euchromatic regions and through regulating replication timing. Indeed, euchromatic zones enriched in H3K4me2 are the preferred sites for pre-RC binding in early replication. Remarkably, LSD1 deficiency leads to a genome-wide switch from early to late in replication timing. We showed that LSD1-promoted DNA replication is mechanistically linked to the loading of TICRR (TopBP1-Interacting Checkpoint and Replication Regulator) onto the pre-RC and subsequent recruitment of the initiator Cdc45 during origin firing. Together, these results reveal an unexpected role for LSD1 in euchromatic origin firing and replication timing.
2022-03-07 | GSE157468 | GEO