Nonhomologous DNA end joining （NHEJ） is the primary pathway for repair of double-strand DNA breaks in human cells and in multicellular eukaryotes. The causes of double-strand breaks often fragment the DNA at the sit...Nonhomologous DNA end joining （NHEJ） is the primary pathway for repair of double-strand DNA breaks in human cells and in multicellular eukaryotes. The causes of double-strand breaks often fragment the DNA at the site of damage, resulting in the loss of information there. NHEJ does not restore the lost information and may resect additional nucleotides during the repair process. The ability to repair a wide range of overhang and damage configurations reflects the flexibility of the nuclease, polymerases, and ligase of NHEJ. The flexibility of the individual components also explains the large number of ways in which NHEJ can repair any given pair of DNA ends. The loss of information locally at sites of NHEJ repair may contribute to cancer and aging, but the action by NHEJ ensures that entire segments of chromosomes are not lost.展开更多
DNA double-strand breaks （DSBs） are introduced in cells by ionizing radiation and reactive oxygen species. In addition, they are commonly generated during V（D）J recombination, an essential aspect of the developing...DNA double-strand breaks （DSBs） are introduced in cells by ionizing radiation and reactive oxygen species. In addition, they are commonly generated during V（D）J recombination, an essential aspect of the developing immune system. Failure to effectively repair these DSBs can result in chromosome breakage, cell death, onset of cancer, and defects in the immune system of higher vertebrates. Fortunately, all mammalian cells possess two enzymatic pathways that mediate the repair of DSBs： homologous recombination and non-homologous end-joining （NHEJ）. The NHEJ process utilizes enzymes that capture both ends of the broken DNA molecule, bring them together in a synaptic DNA-protein complex, and finally repair the DNA break. In this review, all the known enzymes that play a role in the NHEJ process are discussed and a working model for the co-operation of these enzymes during DSB repair is presented.展开更多
乙型肝炎病毒(hepatitis B virus,HBV)编码的X蛋白(hepatitis B virus X protein,HBx)对HBV感染的启始和维持至关重要。HBx可能作为病毒来源的接头分子,介导Cullin-RING E3泛素连接酶4(CullinRING ubiquitin E3ligase 4,CRL4)复合物对...乙型肝炎病毒(hepatitis B virus,HBV)编码的X蛋白(hepatitis B virus X protein,HBx)对HBV感染的启始和维持至关重要。HBx可能作为病毒来源的接头分子,介导Cullin-RING E3泛素连接酶4(CullinRING ubiquitin E3ligase 4,CRL4)复合物对染色体外DNA限制因子SMC5/6的降解。最近研究发现,CRL4接头分子DNA损伤结合蛋白1(DNA damage-binding protein 1,DDB1)可不依赖与HBx的相互作用而直接上调病毒的表达和复制。本研究基于HBx基因删除(X-null)的HBV重组共价闭合环状DNA(recombinant covalently closed circular DNA,rcccDNA)模型系统,在多种体外培养肝细胞系中证实上述发现。有意思的是,CRL4刺激rcccDNAX-null转染细胞抗原分泌表达的效应能被血清饥饿实验抵消。应用尾静脉高压注射小鼠模型,同样发现CRL4并不上调rcccDNAX-null在非增殖小鼠肝脏细胞中的表达。以上结果提示,细胞增殖特征与CRL4不依赖HBx上调病毒抗原分泌表达的效应密切相关,有助于HBx生物学意义的准确分析和理解。展开更多
DNA double-strand breaks(DSBs)are one of the most lethal forms of DNA damage that is not efficiently repaired in prokaryotes.Certain microorganisms can handle chromosomal DSBs using the error-prone non-homologous end ...DNA double-strand breaks(DSBs)are one of the most lethal forms of DNA damage that is not efficiently repaired in prokaryotes.Certain microorganisms can handle chromosomal DSBs using the error-prone non-homologous end joining(NHEJ)system and ultimately cause genome mutagenesis.Here,we demonstrated that Enterobacteria phage T4 DNA ligase alone is capable of mediating in vivo chromosome DSBs repair in Escherichia coli.The ligation efficiency of DSBs with T4 DNA ligase is one order of magnitude higher than the NHEJ system from Mycobacterium tuberculosis.This process introduces chromosome DNA excision with different sizes,which can be manipulated by regulating the activity of host-exonuclease RecBCD.The DNA deletion length reduced either by inactivating recB or expressing the RecBCD inhibitor Gam protein fromλphage.Furthermore,we also found single nucleotide substitutions at the DNA junction,suggesting that T4 DNA ligase,as a single component non-homologous end joining system,has great potential in genome mutagenesis,genome reduction and genome editing.展开更多
A novel method has been developed to monitor the nucleic acids ligation process. Molecular beacon was employed here to convert the ligation information into fluo-rescence signal quickly and quantitatively. This method...A novel method has been developed to monitor the nucleic acids ligation process. Molecular beacon was employed here to convert the ligation information into fluo-rescence signal quickly and quantitatively. This method pro-vides effective and original approach to researching the dy-namic ligation process and the interactions between nucleic acids and ligase. An analytical method for T4 DNA ligase based on this way has been built up with a linear detection range from 2.3×10-4 U/mL to 0.23 U/mL. It is rapid and sensitive to detect 2.8×10-5 U T4 DNA ligase in 10 min.展开更多
文摘Nonhomologous DNA end joining （NHEJ） is the primary pathway for repair of double-strand DNA breaks in human cells and in multicellular eukaryotes. The causes of double-strand breaks often fragment the DNA at the site of damage, resulting in the loss of information there. NHEJ does not restore the lost information and may resect additional nucleotides during the repair process. The ability to repair a wide range of overhang and damage configurations reflects the flexibility of the nuclease, polymerases, and ligase of NHEJ. The flexibility of the individual components also explains the large number of ways in which NHEJ can repair any given pair of DNA ends. The loss of information locally at sites of NHEJ repair may contribute to cancer and aging, but the action by NHEJ ensures that entire segments of chromosomes are not lost.
文摘DNA double-strand breaks （DSBs） are introduced in cells by ionizing radiation and reactive oxygen species. In addition, they are commonly generated during V（D）J recombination, an essential aspect of the developing immune system. Failure to effectively repair these DSBs can result in chromosome breakage, cell death, onset of cancer, and defects in the immune system of higher vertebrates. Fortunately, all mammalian cells possess two enzymatic pathways that mediate the repair of DSBs： homologous recombination and non-homologous end-joining （NHEJ）. The NHEJ process utilizes enzymes that capture both ends of the broken DNA molecule, bring them together in a synaptic DNA-protein complex, and finally repair the DNA break. In this review, all the known enzymes that play a role in the NHEJ process are discussed and a working model for the co-operation of these enzymes during DSB repair is presented.
文摘乙型肝炎病毒(hepatitis B virus,HBV)编码的X蛋白(hepatitis B virus X protein,HBx)对HBV感染的启始和维持至关重要。HBx可能作为病毒来源的接头分子,介导Cullin-RING E3泛素连接酶4(CullinRING ubiquitin E3ligase 4,CRL4)复合物对染色体外DNA限制因子SMC5/6的降解。最近研究发现,CRL4接头分子DNA损伤结合蛋白1(DNA damage-binding protein 1,DDB1)可不依赖与HBx的相互作用而直接上调病毒的表达和复制。本研究基于HBx基因删除(X-null)的HBV重组共价闭合环状DNA(recombinant covalently closed circular DNA,rcccDNA)模型系统,在多种体外培养肝细胞系中证实上述发现。有意思的是,CRL4刺激rcccDNAX-null转染细胞抗原分泌表达的效应能被血清饥饿实验抵消。应用尾静脉高压注射小鼠模型,同样发现CRL4并不上调rcccDNAX-null在非增殖小鼠肝脏细胞中的表达。以上结果提示,细胞增殖特征与CRL4不依赖HBx上调病毒抗原分泌表达的效应密切相关,有助于HBx生物学意义的准确分析和理解。
基金This work was supported by grants from the National Natural Science Foundation of China[31730003,31670077]Natural Science Foundation of Shandong Province[ZR2017ZB0210].
文摘DNA double-strand breaks(DSBs)are one of the most lethal forms of DNA damage that is not efficiently repaired in prokaryotes.Certain microorganisms can handle chromosomal DSBs using the error-prone non-homologous end joining(NHEJ)system and ultimately cause genome mutagenesis.Here,we demonstrated that Enterobacteria phage T4 DNA ligase alone is capable of mediating in vivo chromosome DSBs repair in Escherichia coli.The ligation efficiency of DSBs with T4 DNA ligase is one order of magnitude higher than the NHEJ system from Mycobacterium tuberculosis.This process introduces chromosome DNA excision with different sizes,which can be manipulated by regulating the activity of host-exonuclease RecBCD.The DNA deletion length reduced either by inactivating recB or expressing the RecBCD inhibitor Gam protein fromλphage.Furthermore,we also found single nucleotide substitutions at the DNA junction,suggesting that T4 DNA ligase,as a single component non-homologous end joining system,has great potential in genome mutagenesis,genome reduction and genome editing.
文摘A novel method has been developed to monitor the nucleic acids ligation process. Molecular beacon was employed here to convert the ligation information into fluo-rescence signal quickly and quantitatively. This method pro-vides effective and original approach to researching the dy-namic ligation process and the interactions between nucleic acids and ligase. An analytical method for T4 DNA ligase based on this way has been built up with a linear detection range from 2.3×10-4 U/mL to 0.23 U/mL. It is rapid and sensitive to detect 2.8×10-5 U T4 DNA ligase in 10 min.
