000K utf8 1100 2022$c2022-07-06 1500 eng 2050 urn:nbn:de:hbz:465-20220916-104720-3 2051 10.3390/ijms23147506 3000 Soni, Aashish 3010 Duan, Xiaolu 3010 Iliakis, George 3010 Stuschke, Martin 4000 ATR Contributes More Than ATM in Intra-S-Phase Checkpoint Activation after IR, and DNA-PKcs Facilitates Recovery$dEvidence for Modular Integration of ATM/ATR/DNA-PKcs Functions [Soni, Aashish] 4209 The intra-S-phase checkpoint was among the first reported cell cycle checkpoints in mammalian cells. It transiently slows down the rate of DNA replication after DNA damage to facilitate repair and thus prevents genomic instability. The ionizing radiation (IR)-induced intra-S-phase checkpoint in mammalian cells is thought to be mainly dependent upon the kinase activity of ATM. Defects in the intra-S-phase checkpoint result in radio-resistant DNA synthesis (RDS), which promotes genomic instability. ATM belongs to the PI3K kinase family along with ATR and DNA-PKcs. ATR has been shown to be the key kinase for intra-S-phase checkpoint signaling in yeast and has also been implicated in this checkpoint in higher eukaryotes. Recently, contributions of DNA-PKcs to IR-induced G 2 -checkpoint could also be established. Whether and how ATR and DNA-PKcs are involved in the IR-induced intra-S-phase checkpoint in mammalian cells is incompletely characterized. Here, we investigated the contributions of ATM, ATR, and DNA-PKcs to intra-S-phase checkpoint activation after exposure to IR of human and hamster cells. The results suggest that the activities of both ATM and ATR are essential for efficient intra-S-phase checkpoint activation. Indeed, in a wild-type genetic background, ATR inhibition generates stronger checkpoint defects than ATM inhibition. Similar to G2 checkpoint, DNA-PKcs contributes to the recovery from the intra-S-phase checkpoint. DNA-PKcs–deficient cells show persistent, mainly ATR-dependent intra-S-phase checkpoints. A correlation between the degree of DSB end resection and the strength of the intra-S-phase checkpoint is observed, which again compares well to the G2 checkpoint response. We conclude that the organization of the intra-S-phase checkpoint has a similar mechanistic organization to that of the G 2 checkpoint in cells irradiated in the G 2 phase. 4950 https://doi.org/10.3390/ijms23147506$xR$3Volltext$534 4950 https://nbn-resolving.org/urn:nbn:de:hbz:465-20220916-104720-3$xR$3Volltext$534 4961 https://duepublico2.uni-due.de/receive/duepublico_mods_00076669 5051 610 5550 ATM 5550 ATR 5550 DNA Double Strand Breaks (DSB) 5550 DNA-PK 5550 DSB end resection (resection) 5550 intra-S-phase checkpoint 5550 ionizing radiation (IR)