DNA replication is tightly regulated during the S phase of the cell cycle, and the activation of the intra-S-phase checkpoint due to DNA damage usually results in arrest of DNA synthesis. However, the molecular detail...DNA replication is tightly regulated during the S phase of the cell cycle, and the activation of the intra-S-phase checkpoint due to DNA damage usually results in arrest of DNA synthesis. However, the molecular details about the correlation between the checkpoint and regulation of DNA replication are still unclear. To investigate the connections between DNA replication and DNA damage checkpoint, a DNA-damage reagent, tripchlorolide, was applied to CHO (Chinese ovary hamster) cells at early- or middle-stages of the S phase. The early-S-phase treatment with TC significantly delayed the progression of the S phase and caused the phosphorylation of the Chk1 checkpoint protein, whereas the middle-S-phase treatment only slightly slowed down the progression of the S phase. Furthermore, the analysis of DNA replication patterns revealed that replication pattern Ⅱ was greatly prolonged in the cells treated with the drug during the early-S phase, whereas the late-replication patterns of these cells were hardly detected, suggesting that the activation of the intra-S-phase checkpoint inhibits the late-origin firing of DNA replication. We conclude that cells at different stages of the S phase are differentially sensitive to the DNA-damage reagent, and the activation of the intra-Sphase checkpoint blocks the DNA replication progression in the late stage of S phase.展开更多
Objective:The open-label,phase II RATIONALE-209 study evaluated tislelizumab(anti-programmed cell death protein 1 antibody)as a tissue-agnostic monotherapy for microsatellite instability-high(MSI-H)/mismatch repair-de...Objective:The open-label,phase II RATIONALE-209 study evaluated tislelizumab(anti-programmed cell death protein 1 antibody)as a tissue-agnostic monotherapy for microsatellite instability-high(MSI-H)/mismatch repair-deficient(dMMR)tumors.Methods:Adults with previously treated,locally advanced unresectable or metastatic MSI-H/dMMR solid tumors were enrolled.Patients received tislelizumab 200 mg intravenously every 3 weeks.Objective response rate(ORR;primary endpoint),duration of response(DoR),and progression-free survival(PFS)were assessed by independent review committee(Response Evaluation Criteria in Solid Tumors v1.1).Results:Eighty patients were enrolled and treated;75(93.8%)patients had measurable disease at baseline.Most had metastatic disease and received at least one prior therapy for advanced/metastatic disease(n=79;98.8%).At primary analysis(data cutoff July 8,2021;median follow-up 15.2 months),overall ORR[46.7%;95%confidence interval(95%CI),35.1−58.6;one-sided P<0.0001]and ORR across tumor-specific subgroups[colorectal(n=46):39.1%(95%CI,25.1–54.6);gastric/gastroesophageal junction(n=9):55.6%(95%CI,21.2−86.3);others(n=20):60.0%(95%CI,36.1−80.9)]were significantly greater with tislelizumab vs.a prespecified historical control ORR of 10%;five(6.7%)patients had complete responses.Median DoR,PFS,and overall survival were not reached with long-term follow-up(data cutoff December 5,2022;median follow-up 28.9 months).Tislelizumab was well tolerated with no unexpected safety signals.Treatment-related adverse events(TRAEs)of grade≥3 occurred in 53.8%of patients;7.5%of patients discontinued treatment due to TRAEs.Conclusions:Tislelizumab demonstrated a significant ORR improvement in patients with previously treated,locally advanced unresectable or metastatic MSI-H/dMMR tumors and was generally well tolerated.展开更多
Chromosomal DNA replication is one of the central biological events occurring inside cells.Due to its large size,the replication of genomic DNA in eukaryotes initiates at hundreds to tens of thousands of sites called ...Chromosomal DNA replication is one of the central biological events occurring inside cells.Due to its large size,the replication of genomic DNA in eukaryotes initiates at hundreds to tens of thousands of sites called DNA origins so that the replication could be completed in a limited time.Further,eukaryotic DNA replication is sophisticatedly regulated,and this regulation guarantees that each origin fires once per S phase and each segment of DNA gets duplication also once per cell cycle.The first step of replication initiation is the assembly of pre-replication complex(pre-RC).Since 1973,four proteins,Cdc6/Cdc18,MCM,ORC and Cdt1,have been extensively studied and proved to be pre-RC components.Recently,a novel pre-RC component called Sap1/Girdin was identified.Sap1/Girdin is required for loading Cdc18/Cdc6 to origins for pre-RC assembly in the fission yeast and human cells,respectively.At the transition of G1 to S phase,pre-RC is activated by the two kinases,cyclin-dependent kinase(CDK)and Dbf4-dependent kinase(DDK),and subsequently,RPA,primase-polα,PCNA,topoisomerase,Cdc45,polδ,and polεare recruited to DNA origins for creating two bi-directional replication forks and initiating DNA replication.As replication forks move along chromatin DNA,they frequently stall due to the presence of a great number of replication barriers on chromatin DNA,such as secondary DNA structures,protein/DNA complexes,DNA lesions,gene transcription.Stalled forks must require checkpoint regulation for their stabilization.Otherwise,stalled forks will collapse,which results in incomplete DNA replication and genomic instability.This short review gives a concise introduction regarding the current understanding of replication initiation and replication fork stabilization.展开更多
基金This work was supported by a grant from the National Natural Science Foundation of China(No.30230110)a special grant from the Major State Basic Research Pro-gram of China(No.G1999053901)a grant from the Chinese Academy of Sciences(No.KSCX2-SW-203)to Jia Rui WU.
文摘DNA replication is tightly regulated during the S phase of the cell cycle, and the activation of the intra-S-phase checkpoint due to DNA damage usually results in arrest of DNA synthesis. However, the molecular details about the correlation between the checkpoint and regulation of DNA replication are still unclear. To investigate the connections between DNA replication and DNA damage checkpoint, a DNA-damage reagent, tripchlorolide, was applied to CHO (Chinese ovary hamster) cells at early- or middle-stages of the S phase. The early-S-phase treatment with TC significantly delayed the progression of the S phase and caused the phosphorylation of the Chk1 checkpoint protein, whereas the middle-S-phase treatment only slightly slowed down the progression of the S phase. Furthermore, the analysis of DNA replication patterns revealed that replication pattern Ⅱ was greatly prolonged in the cells treated with the drug during the early-S phase, whereas the late-replication patterns of these cells were hardly detected, suggesting that the activation of the intra-S-phase checkpoint inhibits the late-origin firing of DNA replication. We conclude that cells at different stages of the S phase are differentially sensitive to the DNA-damage reagent, and the activation of the intra-Sphase checkpoint blocks the DNA replication progression in the late stage of S phase.
基金sponsored by BeiGene.Third-party medical writing assistance was provided by Ghina Yaacoub,MSc,of Ashfield MedComms,an Inizio Company,and funded by BeiGene.
文摘Objective:The open-label,phase II RATIONALE-209 study evaluated tislelizumab(anti-programmed cell death protein 1 antibody)as a tissue-agnostic monotherapy for microsatellite instability-high(MSI-H)/mismatch repair-deficient(dMMR)tumors.Methods:Adults with previously treated,locally advanced unresectable or metastatic MSI-H/dMMR solid tumors were enrolled.Patients received tislelizumab 200 mg intravenously every 3 weeks.Objective response rate(ORR;primary endpoint),duration of response(DoR),and progression-free survival(PFS)were assessed by independent review committee(Response Evaluation Criteria in Solid Tumors v1.1).Results:Eighty patients were enrolled and treated;75(93.8%)patients had measurable disease at baseline.Most had metastatic disease and received at least one prior therapy for advanced/metastatic disease(n=79;98.8%).At primary analysis(data cutoff July 8,2021;median follow-up 15.2 months),overall ORR[46.7%;95%confidence interval(95%CI),35.1−58.6;one-sided P<0.0001]and ORR across tumor-specific subgroups[colorectal(n=46):39.1%(95%CI,25.1–54.6);gastric/gastroesophageal junction(n=9):55.6%(95%CI,21.2−86.3);others(n=20):60.0%(95%CI,36.1−80.9)]were significantly greater with tislelizumab vs.a prespecified historical control ORR of 10%;five(6.7%)patients had complete responses.Median DoR,PFS,and overall survival were not reached with long-term follow-up(data cutoff December 5,2022;median follow-up 28.9 months).Tislelizumab was well tolerated with no unexpected safety signals.Treatment-related adverse events(TRAEs)of grade≥3 occurred in 53.8%of patients;7.5%of patients discontinued treatment due to TRAEs.Conclusions:Tislelizumab demonstrated a significant ORR improvement in patients with previously treated,locally advanced unresectable or metastatic MSI-H/dMMR tumors and was generally well tolerated.
文摘Chromosomal DNA replication is one of the central biological events occurring inside cells.Due to its large size,the replication of genomic DNA in eukaryotes initiates at hundreds to tens of thousands of sites called DNA origins so that the replication could be completed in a limited time.Further,eukaryotic DNA replication is sophisticatedly regulated,and this regulation guarantees that each origin fires once per S phase and each segment of DNA gets duplication also once per cell cycle.The first step of replication initiation is the assembly of pre-replication complex(pre-RC).Since 1973,four proteins,Cdc6/Cdc18,MCM,ORC and Cdt1,have been extensively studied and proved to be pre-RC components.Recently,a novel pre-RC component called Sap1/Girdin was identified.Sap1/Girdin is required for loading Cdc18/Cdc6 to origins for pre-RC assembly in the fission yeast and human cells,respectively.At the transition of G1 to S phase,pre-RC is activated by the two kinases,cyclin-dependent kinase(CDK)and Dbf4-dependent kinase(DDK),and subsequently,RPA,primase-polα,PCNA,topoisomerase,Cdc45,polδ,and polεare recruited to DNA origins for creating two bi-directional replication forks and initiating DNA replication.As replication forks move along chromatin DNA,they frequently stall due to the presence of a great number of replication barriers on chromatin DNA,such as secondary DNA structures,protein/DNA complexes,DNA lesions,gene transcription.Stalled forks must require checkpoint regulation for their stabilization.Otherwise,stalled forks will collapse,which results in incomplete DNA replication and genomic instability.This short review gives a concise introduction regarding the current understanding of replication initiation and replication fork stabilization.
