Recent studies have mapped key genetic changes in colorectal cancer(CRC)that impact important pathways contributing to the multistep models for CRC initiation and development.In parallel with genetic changes,normal an...Recent studies have mapped key genetic changes in colorectal cancer(CRC)that impact important pathways contributing to the multistep models for CRC initiation and development.In parallel with genetic changes,normal and cancer tissues harbor epigenetic alterations impacting regulation of critical genes that have been shown to play profound roles in the tumor initiation.Cumulatively,these molecular changes are only loosely associated with heterogenous transcriptional programs,reflecting the heterogeneity in the various CRC molecular subtypes and the paths to CRC development.Studies from mapping molecular alterations in early CRC lesions and use of experimental models suggest that the intricate dependencies of various genetic and epigenetic hits shape the early development of CRC via different pathways and its manifestation into various CRC subtypes.We highlight the dependency of epigenetic and genetic changes in driving CRC development and discuss factors affecting epigenetic alterations over time and,by extension,risk for cancer.展开更多
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
p53 is a key transcription factor to regulate gene transcription.However,the molecular mechanism of chromatin-associated p53 on gene transcription remains elusive.Here,using unbiased protein affinity purification,we f...p53 is a key transcription factor to regulate gene transcription.However,the molecular mechanism of chromatin-associated p53 on gene transcription remains elusive.Here,using unbiased protein affinity purification,we found that the RNF20/40 complex associated with p53 on the chromatin.Further analyses indicated that p53 mediated the recruitment of the RNF20/40 complex to p53 target gene loci including p21 and PUMA loci and regulated the transcription of p21 and PUMA via the RNF20/40 complex-dependent histone H2B ubiquitination(ubH2B).Lacking the RNF20/40 complex suppressed not only ubH2B but also the generation of the mature mRNA of p21 and PUMA.Moreover,ubH2B was recognized by the ubiquitin-binding motif of pre-mRNA processing splicing factor 8(PRPF8),a subunit in the spliceosome,and PRPF8 was required for the maturation of the mRNA of p21 and PUMA.Our study unveils a novel p53-dependent pathway that regulates mRNA splicing for tumor suppression.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
Mammalian topoisomerase 1（TOP1） is an essential enzyme for normal development.TOP1 relaxes supercoiled DNA to remove helical constraints that can otherwise hinder DNA replication and transcription and thus block cel...Mammalian topoisomerase 1（TOP1） is an essential enzyme for normal development.TOP1 relaxes supercoiled DNA to remove helical constraints that can otherwise hinder DNA replication and transcription and thus block cell growth.Unfortunately,this exact activity can covalently trap TOP1 on the DNA that could lead to cell death or mutagenesis,a precursor for tumorigenesis.It is therefore important for cells to find a proper balance between the utilization of the TOP1 catalytic activity to maintain DNA topology and the risk of accumulating the toxic DNA damages due to TOP1 trapping that prevents normal cell growth.In an apparent contradiction to the negative attribute of the TOP1 activity to genome stability,the detrimental effect of the TOP1-induced DNA lesions on cell survival has made this enzyme a prime target for cancer therapies to kill fast-growing cancer cells.In addition,cumulative evidence supports a direct role of TOP1 in promoting transcriptional progression independent of its topoisomerase activity.The involvement of TOP1 in transcriptional regulation has recently become a focus in developing potential new treatments for a subtype of autism spectrum disorders.Clearly,the impact of TOP1 on human health is multifold.In this review,we will summarize our current understandings on how TOP1 contributes to human diseases and how its activity is targeted for disease treatments.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
Protein poly ADP-ribosylation（PARylation） is a widespread post-translational modification at DNA lesions,which is catalyzed by poly（ADP-ribose） polymerases（PARPs）.This modification regulates a number of biologic...Protein poly ADP-ribosylation（PARylation） is a widespread post-translational modification at DNA lesions,which is catalyzed by poly（ADP-ribose） polymerases（PARPs）.This modification regulates a number of biological processes including chromatin reorganization,DNA damage response（DDR）,transcriptional regulation,apoptosis,and mitosis.PARP1,functioning as a DNA damage sensor,can be activated by DNA lesions,forming PAR chains that serve as a docking platform for DNA repair factors with high biochemical complexity.Here,we highlight molecular insights into PARylation recognition,the expanding role of PARylation in DDR pathways,and the functional interaction between PARylation and ubiquitination,which will offer us a better understanding of the biological roles of this unique post-translational modification.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
Introduction:Plasma circulating tumor DNA(ctDNA)is an ideal approach to detecting the epidermal growth factor receptor(EGFR)T790M mutation,which is a major mechanism of resistance to first-generation EGFR-tyrosine kin...Introduction:Plasma circulating tumor DNA(ctDNA)is an ideal approach to detecting the epidermal growth factor receptor(EGFR)T790M mutation,which is a major mechanism of resistance to first-generation EGFR-tyrosine kinase inhibitor(TKI)therapy.The present study aimed to explore the association of ctDNA-identified T790M mutation with disease failure sites and clinical prognosis in non-small cell lung cancer(NSCLC)patients.Methods:Patients who progressed on first-generation TKIs were categorized into failure site groups of chest limited(CF),brain limited(BF)and other(OF).Amplification refractory mutation system(ARMS)and droplet digital PCR(ddPCR)were used to identify the T790M mutation in ctDNA.Prognosis was analyzed with Kaplan-Meier methods.Results:Overall concordance between the two methods was 78.3%.According to both ARMS and ddPCR,patients in the OF group had a significantly higher rate of T790M mutation than did patients in the BF and CF groups(P<0.001),and a significantly higher T790M mutation rate was also observed in OF-group patients than in those in the CF and BF groups(P<0.001).AZD9291 was found to be an excellent treatment option and yielded the longest survival for T790M+patients in all groups who had progressed on EGFR-TKIs;for other treatments,the prognosis of T790M−patient subgroups varied.Conclusions:The present study demonstrates that T790M mutation in ctDNA is associated with failure sites for NSCLC patients after EGFR-TKI therapy and indicates that both failure site and T790M mutational status greatly influ-ence treatment selection and prognosis.展开更多
基金supported by the National Cancer Institute and National Institute on Aging at the National Institutes of Health[NIH/NCI R01CA229240,NIH U01AG066101]。
文摘Recent studies have mapped key genetic changes in colorectal cancer(CRC)that impact important pathways contributing to the multistep models for CRC initiation and development.In parallel with genetic changes,normal and cancer tissues harbor epigenetic alterations impacting regulation of critical genes that have been shown to play profound roles in the tumor initiation.Cumulatively,these molecular changes are only loosely associated with heterogenous transcriptional programs,reflecting the heterogeneity in the various CRC molecular subtypes and the paths to CRC development.Studies from mapping molecular alterations in early CRC lesions and use of experimental models suggest that the intricate dependencies of various genetic and epigenetic hits shape the early development of CRC via different pathways and its manifestation into various CRC subtypes.We highlight the dependency of epigenetic and genetic changes in driving CRC development and discuss factors affecting epigenetic alterations over time and,by extension,risk for cancer.
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This work was supported by the National Natural Science Foundation of China(31670812 to C.W.)the grant for Returned Overseas Chinese Scholars of Hebei Province(CY201602 to C.W.)+1 种基金the Hundreds of Outstanding Talent Innovation Projects in Hebei Province(SLRC2017023 to C.W.)the Natural Science Foundation of Hebei Province(C2018201171 to C.W.).
文摘p53 is a key transcription factor to regulate gene transcription.However,the molecular mechanism of chromatin-associated p53 on gene transcription remains elusive.Here,using unbiased protein affinity purification,we found that the RNF20/40 complex associated with p53 on the chromatin.Further analyses indicated that p53 mediated the recruitment of the RNF20/40 complex to p53 target gene loci including p21 and PUMA loci and regulated the transcription of p21 and PUMA via the RNF20/40 complex-dependent histone H2B ubiquitination(ubH2B).Lacking the RNF20/40 complex suppressed not only ubH2B but also the generation of the mature mRNA of p21 and PUMA.Moreover,ubH2B was recognized by the ubiquitin-binding motif of pre-mRNA processing splicing factor 8(PRPF8),a subunit in the spliceosome,and PRPF8 was required for the maturation of the mRNA of p21 and PUMA.Our study unveils a novel p53-dependent pathway that regulates mRNA splicing for tumor suppression.
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supported by a funding from the National Cancer Institute (Grant No.R01 CA151245),the United States
文摘Mammalian topoisomerase 1（TOP1） is an essential enzyme for normal development.TOP1 relaxes supercoiled DNA to remove helical constraints that can otherwise hinder DNA replication and transcription and thus block cell growth.Unfortunately,this exact activity can covalently trap TOP1 on the DNA that could lead to cell death or mutagenesis,a precursor for tumorigenesis.It is therefore important for cells to find a proper balance between the utilization of the TOP1 catalytic activity to maintain DNA topology and the risk of accumulating the toxic DNA damages due to TOP1 trapping that prevents normal cell growth.In an apparent contradiction to the negative attribute of the TOP1 activity to genome stability,the detrimental effect of the TOP1-induced DNA lesions on cell survival has made this enzyme a prime target for cancer therapies to kill fast-growing cancer cells.In addition,cumulative evidence supports a direct role of TOP1 in promoting transcriptional progression independent of its topoisomerase activity.The involvement of TOP1 in transcriptional regulation has recently become a focus in developing potential new treatments for a subtype of autism spectrum disorders.Clearly,the impact of TOP1 on human health is multifold.In this review,we will summarize our current understandings on how TOP1 contributes to human diseases and how its activity is targeted for disease treatments.
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funded by the National Institutes of Health of the United States(Grant Nos.CA132755,CA187209,and GM108647)
文摘Protein poly ADP-ribosylation（PARylation） is a widespread post-translational modification at DNA lesions,which is catalyzed by poly（ADP-ribose） polymerases（PARPs）.This modification regulates a number of biological processes including chromatin reorganization,DNA damage response（DDR）,transcriptional regulation,apoptosis,and mitosis.PARP1,functioning as a DNA damage sensor,can be activated by DNA lesions,forming PAR chains that serve as a docking platform for DNA repair factors with high biochemical complexity.Here,we highlight molecular insights into PARylation recognition,the expanding role of PARylation in DDR pathways,and the functional interaction between PARylation and ubiquitination,which will offer us a better understanding of the biological roles of this unique post-translational modification.
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supported by grants from Projects of Medical and Health Technology in Zhejiang Province(WKJ-2J-1532)the Zhejiang Provincial Natural Science Foundation(LY15H160010)National Natural Science Foundation of China(Grant No.81602671).
文摘Introduction:Plasma circulating tumor DNA(ctDNA)is an ideal approach to detecting the epidermal growth factor receptor(EGFR)T790M mutation,which is a major mechanism of resistance to first-generation EGFR-tyrosine kinase inhibitor(TKI)therapy.The present study aimed to explore the association of ctDNA-identified T790M mutation with disease failure sites and clinical prognosis in non-small cell lung cancer(NSCLC)patients.Methods:Patients who progressed on first-generation TKIs were categorized into failure site groups of chest limited(CF),brain limited(BF)and other(OF).Amplification refractory mutation system(ARMS)and droplet digital PCR(ddPCR)were used to identify the T790M mutation in ctDNA.Prognosis was analyzed with Kaplan-Meier methods.Results:Overall concordance between the two methods was 78.3%.According to both ARMS and ddPCR,patients in the OF group had a significantly higher rate of T790M mutation than did patients in the BF and CF groups(P<0.001),and a significantly higher T790M mutation rate was also observed in OF-group patients than in those in the CF and BF groups(P<0.001).AZD9291 was found to be an excellent treatment option and yielded the longest survival for T790M+patients in all groups who had progressed on EGFR-TKIs;for other treatments,the prognosis of T790M−patient subgroups varied.Conclusions:The present study demonstrates that T790M mutation in ctDNA is associated with failure sites for NSCLC patients after EGFR-TKI therapy and indicates that both failure site and T790M mutational status greatly influ-ence treatment selection and prognosis.
