AIM To test whether Nox1 plays a role in typhlitis induced by Salmonella enterica serovar Typhimurium(S. Tm) in a mouse model.METHODS Eight-week-old male wild-type(WT) and Nox1 knockout(KO) C57BL6/J(B6) mice were admi...AIM To test whether Nox1 plays a role in typhlitis induced by Salmonella enterica serovar Typhimurium(S. Tm) in a mouse model.METHODS Eight-week-old male wild-type(WT) and Nox1 knockout(KO) C57BL6/J(B6) mice were administered metronidazole water for 4 d to make them susceptible to S. Tm infection by the oral route. The mice were given plain water and administered with 4 different doses of S. Tm by oral gavage. The mice were followed for another 4 d. From the time of the metronidazole application, the mice were observed twice daily and weighed daily. The ileum, cecum and colon were removed for sampling at the fourth day post-inoculation. Portions of all three tissues were fixed for histology and placed in RNAlater for m RNA/c DNA preparation and quantitative real-time PCR. The contents of the cecum were recovered for estimation of S. Tm CFU.RESULTS We found Nox1-knockout(Nox1-KO) mice were not more sensitive to S. Tm colonization and infection than WT B6 mice. This conclusion is based on the following observations:(1) S. Tm-infection induced similar weight loss in Nox1-KO mice compared to WT mice;(2) the same S. Tm CFU was recovered from the cecal content of Nox1-KO and WT mice regardless of the inoculation dose, except the lowest inoculation dose(2 × 106 CFU) for which the Nox1-KO had one-log lower CFU than WT mice;(3) there is no difference in cecal pathology between WT and Nox1-KO groups; and(4) there are no S. Tm infection-induced changes in gene expression levels(IL-1b, TNF-α, and Duox2) between WT and Nox1-KO groups. The Alpi gene expression was more suppressed by S. Tm treatment in WT than the Nox1-KO cecum. CONCLUSION Nox1 does not protect mice from S. Tm colonization. Nox1-KO provides a very minor protective effect against S. Tm infection. Using NOX1-specific inhibitors for colitis therapy should not increase risks in bacterial infection.展开更多
Completion of lagging strand DNA synthesis requires processing of up to 50 million Okazaki fragments per cell cycle in mammalian cells.Even in yeast,the Okazaki fragment maturation happens approximately a million time...Completion of lagging strand DNA synthesis requires processing of up to 50 million Okazaki fragments per cell cycle in mammalian cells.Even in yeast,the Okazaki fragment maturation happens approximately a million times during a single round of DNA replication.Therefore,efficient processing of Okazaki fragments is vital for DNA replication and cell proliferation.During this process,primase-synthesized RNA/DNA primers are removed,and Okazaki fragments are joined into an intact lagging strand DNA.The processing of RNA/DNA primers requires a group of structure-specific nucleases typified by flap endonuclease 1(FEN1).Here,we sum-marize the distinct roles of these nucleases in different pathways for removal of RNA/DNA primers.Recent findings reveal that Okazaki fragment maturation is highly coordinated.The dynamic interactions of polymerase d,FEN1 and DNA ligase I with prolif-erating cell nuclear antigen allow these enzymes to act sequentially during Okazaki fragment maturation.Such protein–protein interactions may be regulated by post-translational modifications.We also discuss studies using mutant mouse models that suggest two distinct cancer etiological mechanisms arising from defects in different steps of Okazaki fragment maturation.Mutations that affect the efficiency of RNA primer removal may result in accumulation of unligated nicks and DNA double-strand breaks.These DNA strand breaks can cause varying forms of chromosome aberrations,contributing to development of cancer that associates with aneuploidy and gross chromosomal rearrangement.On the other hand,mutations that impair editing out of polymerase a incorporation errors result in cancer displaying a strong mutator phenotype.展开更多
Two of the unsolved but important questions in epigenetics are whether arginine demethylases （RDMs） exist and whether proteolytic cleavage of the histone tails and subsequent histone remodeling are a major epigeneti...Two of the unsolved but important questions in epigenetics are whether arginine demethylases （RDMs） exist and whether proteolytic cleavage of the histone tails and subsequent histone remodeling are a major epigenetic modification process. Jumonji domain （JmjC）-containing proteins have been characterized as lysine demethylases （KDMs） in a certain degree （Klose et al., 2006）. Emerging evidences indicate that they also catalyze demethylation reaction on the arginine residues and proteolytic removal of histone tails. These processes are likely associated with biological meanings.展开更多
Human flap endonuclease 1 （FEN1） is a structure-specific, multi-functional endonuclease essential for DNA replication and repair. We and others have shown that during DNA replication, FEN1 processes Okazaki fragment...Human flap endonuclease 1 （FEN1） is a structure-specific, multi-functional endonuclease essential for DNA replication and repair. We and others have shown that during DNA replication, FEN1 processes Okazaki fragments via its interaction with the proliferating cell nuclear antigen （PCNA）. Alternatively, in response to DNA damage, FEN1 interacts with the PCNA-like Radg-Radl-Husl complex instead of PCNA to engage in DNA repair activities, such as homology-directed repair of stalled DNA replication forks. However, it is unclear how FEN1 is able to switch between these interactions and its roles in DNA replication and DNA repair. Here, we report that FEN1 undergoes SUMOylation by SUMO-1 in response to DNA replication fork-staUing agents, such as UV irradiation, hydroxyurea, and mitomycin C. This DNA damage-induced SUMO-1 modification promotes the interaction of FEN1 with the Radg-Rad1-Husl complex. Furthermore, we found that FEN1 mutations that prevent its SUMO-1 modification also impair its ability to interact with HUS1 and to rescue stalled replication forks. These impairments lead to the accumulation of DNA damage and heightened sensitivity to fork-staUing agents. Altogether, our findings suggest an important role of the SUMO-1 modification of FEN1 in regulating its roles in DNA replication and repair.展开更多
The mutation-mediated overexpression of epidermal growth factor receptor tyrosine kinase(EGFR TK)and its activation play an important role in the cellular proliferation and epithelial tumorigenesis.A series of inhibit...The mutation-mediated overexpression of epidermal growth factor receptor tyrosine kinase(EGFR TK)and its activation play an important role in the cellular proliferation and epithelial tumorigenesis.A series of inhibitors targeting the intracellular tyrosine kinase(TK)domain of EGFR have been developed and applied to clinical practice.Although these inhibitors safely and effectively restrain tumor cell proliferation and prolong survival in some patients,acquired resistance ultimately arises.DNA mutations contribute to druginduced cancer-cell resistance.展开更多
Nucleases are a super family of enzymes that hydrolyze phosphodiester bonds present in genomes.They widely vary in substrates,causing differentiation in cleavage patterns and having a diversified role in maintaining g...Nucleases are a super family of enzymes that hydrolyze phosphodiester bonds present in genomes.They widely vary in substrates,causing differentiation in cleavage patterns and having a diversified role in maintaining genetic material.Through cellular evolution of prokaryotic to eukaryotic,nucleases become structure-specific in recognizing its own or foreign genomic DNA/RNA configurations as its substrates,including flaps,bubbles,and Holliday junctions.These special structural configurations are commonly found as intermediates in processes like DNA replication,repair,and recombination.The structure-specific nature and diversified functions make them essential to maintaining genome integrity and evolution in normal and cancer cells.In this article,we review their roles in various pathways,including Okazaki fragment maturation during DNA replication,end resection in homology-directed recombination repair of DNA double-strand breaks,DNA excision repair and apoptosis DNA fragmentation in response to exogenous DNA damage,and HIV life cycle.As the nucleases serve as key points for the DNA dynamics,cellular apoptosis,and cancer cell survival pathways,we discuss the efforts in the field in developing the therapeutic regimens,taking advantage of recently available knowledge of their diversified structures and functions.展开更多
基金Supported by Federal funds from the National Cancer Institute(NCI)under Contract,No.HHSN261200800001E(to Chu FF)Research reported in this publication included work performed in the Animal Resources Center Core supported by the National Cancer Institute of the National Institutes of Health under award No.P30CA033572
文摘AIM To test whether Nox1 plays a role in typhlitis induced by Salmonella enterica serovar Typhimurium(S. Tm) in a mouse model.METHODS Eight-week-old male wild-type(WT) and Nox1 knockout(KO) C57BL6/J(B6) mice were administered metronidazole water for 4 d to make them susceptible to S. Tm infection by the oral route. The mice were given plain water and administered with 4 different doses of S. Tm by oral gavage. The mice were followed for another 4 d. From the time of the metronidazole application, the mice were observed twice daily and weighed daily. The ileum, cecum and colon were removed for sampling at the fourth day post-inoculation. Portions of all three tissues were fixed for histology and placed in RNAlater for m RNA/c DNA preparation and quantitative real-time PCR. The contents of the cecum were recovered for estimation of S. Tm CFU.RESULTS We found Nox1-knockout(Nox1-KO) mice were not more sensitive to S. Tm colonization and infection than WT B6 mice. This conclusion is based on the following observations:(1) S. Tm-infection induced similar weight loss in Nox1-KO mice compared to WT mice;(2) the same S. Tm CFU was recovered from the cecal content of Nox1-KO and WT mice regardless of the inoculation dose, except the lowest inoculation dose(2 × 106 CFU) for which the Nox1-KO had one-log lower CFU than WT mice;(3) there is no difference in cecal pathology between WT and Nox1-KO groups; and(4) there are no S. Tm infection-induced changes in gene expression levels(IL-1b, TNF-α, and Duox2) between WT and Nox1-KO groups. The Alpi gene expression was more suppressed by S. Tm treatment in WT than the Nox1-KO cecum. CONCLUSION Nox1 does not protect mice from S. Tm colonization. Nox1-KO provides a very minor protective effect against S. Tm infection. Using NOX1-specific inhibitors for colitis therapy should not increase risks in bacterial infection.
基金supported by the National Cancer Institute grants R01CA073764 and R01CA085344.
文摘Completion of lagging strand DNA synthesis requires processing of up to 50 million Okazaki fragments per cell cycle in mammalian cells.Even in yeast,the Okazaki fragment maturation happens approximately a million times during a single round of DNA replication.Therefore,efficient processing of Okazaki fragments is vital for DNA replication and cell proliferation.During this process,primase-synthesized RNA/DNA primers are removed,and Okazaki fragments are joined into an intact lagging strand DNA.The processing of RNA/DNA primers requires a group of structure-specific nucleases typified by flap endonuclease 1(FEN1).Here,we sum-marize the distinct roles of these nucleases in different pathways for removal of RNA/DNA primers.Recent findings reveal that Okazaki fragment maturation is highly coordinated.The dynamic interactions of polymerase d,FEN1 and DNA ligase I with prolif-erating cell nuclear antigen allow these enzymes to act sequentially during Okazaki fragment maturation.Such protein–protein interactions may be regulated by post-translational modifications.We also discuss studies using mutant mouse models that suggest two distinct cancer etiological mechanisms arising from defects in different steps of Okazaki fragment maturation.Mutations that affect the efficiency of RNA primer removal may result in accumulation of unligated nicks and DNA double-strand breaks.These DNA strand breaks can cause varying forms of chromosome aberrations,contributing to development of cancer that associates with aneuploidy and gross chromosomal rearrangement.On the other hand,mutations that impair editing out of polymerase a incorporation errors result in cancer displaying a strong mutator phenotype.
文摘Two of the unsolved but important questions in epigenetics are whether arginine demethylases （RDMs） exist and whether proteolytic cleavage of the histone tails and subsequent histone remodeling are a major epigenetic modification process. Jumonji domain （JmjC）-containing proteins have been characterized as lysine demethylases （KDMs） in a certain degree （Klose et al., 2006）. Emerging evidences indicate that they also catalyze demethylation reaction on the arginine residues and proteolytic removal of histone tails. These processes are likely associated with biological meanings.
基金This work was supported by grants from the National Basic Research Program of China （2015CB910600）, the National Natural Science Foundation of China （31700688）, the National Key Research and Development Program of China （2017YFA0503900）, and the Natural Science Foundation of Zhejiang Province （LY16C050003） to Y.I.H. and H.X. A part of the work presented in the current article was supported by the National Institutes of Health grants ROICA073764 to B.H.S and R50CA211397 to L.Z.
文摘Human flap endonuclease 1 （FEN1） is a structure-specific, multi-functional endonuclease essential for DNA replication and repair. We and others have shown that during DNA replication, FEN1 processes Okazaki fragments via its interaction with the proliferating cell nuclear antigen （PCNA）. Alternatively, in response to DNA damage, FEN1 interacts with the PCNA-like Radg-Radl-Husl complex instead of PCNA to engage in DNA repair activities, such as homology-directed repair of stalled DNA replication forks. However, it is unclear how FEN1 is able to switch between these interactions and its roles in DNA replication and DNA repair. Here, we report that FEN1 undergoes SUMOylation by SUMO-1 in response to DNA replication fork-staUing agents, such as UV irradiation, hydroxyurea, and mitomycin C. This DNA damage-induced SUMO-1 modification promotes the interaction of FEN1 with the Radg-Rad1-Husl complex. Furthermore, we found that FEN1 mutations that prevent its SUMO-1 modification also impair its ability to interact with HUS1 and to rescue stalled replication forks. These impairments lead to the accumulation of DNA damage and heightened sensitivity to fork-staUing agents. Altogether, our findings suggest an important role of the SUMO-1 modification of FEN1 in regulating its roles in DNA replication and repair.
基金This work was supported by the National Institutes of Health[R01CA073764 to B.H.S.,R50CA211397 to L.Z.].
文摘The mutation-mediated overexpression of epidermal growth factor receptor tyrosine kinase(EGFR TK)and its activation play an important role in the cellular proliferation and epithelial tumorigenesis.A series of inhibitors targeting the intracellular tyrosine kinase(TK)domain of EGFR have been developed and applied to clinical practice.Although these inhibitors safely and effectively restrain tumor cell proliferation and prolong survival in some patients,acquired resistance ultimately arises.DNA mutations contribute to druginduced cancer-cell resistance.
基金This work was supported by National Institutes of Health(NIH)/National Cancer Institute(NCI)grants(R01CA073764,R01CA085344,and R01CA233664 to B.S.and R50CA211397 to L.Z.)Chinese Academy of Medical Sciences Innovation Fund for Medical Sciences(CIFMS,2023-I2M-3-006 to H.S.).
文摘Nucleases are a super family of enzymes that hydrolyze phosphodiester bonds present in genomes.They widely vary in substrates,causing differentiation in cleavage patterns and having a diversified role in maintaining genetic material.Through cellular evolution of prokaryotic to eukaryotic,nucleases become structure-specific in recognizing its own or foreign genomic DNA/RNA configurations as its substrates,including flaps,bubbles,and Holliday junctions.These special structural configurations are commonly found as intermediates in processes like DNA replication,repair,and recombination.The structure-specific nature and diversified functions make them essential to maintaining genome integrity and evolution in normal and cancer cells.In this article,we review their roles in various pathways,including Okazaki fragment maturation during DNA replication,end resection in homology-directed recombination repair of DNA double-strand breaks,DNA excision repair and apoptosis DNA fragmentation in response to exogenous DNA damage,and HIV life cycle.As the nucleases serve as key points for the DNA dynamics,cellular apoptosis,and cancer cell survival pathways,we discuss the efforts in the field in developing the therapeutic regimens,taking advantage of recently available knowledge of their diversified structures and functions.
