Crystallography, X-Ray ; DNA Repair ; Exodeoxyribonucleases ; chemistry ; Humans ; Protein Conformation

Gene cloning is one of the most important and widely used technologies in molecular biology research. Generally, DNA fragment is cut with restriction enzyme, and then the product is ligated to a linearized vector with complementary sticky end or blunt end by DNA-ligase. This traditional DNA cloning method requires compatible enzyme recognition sites existing in both PCR fragment and targeted vector. Several ligase-free methods have been established to avoid the using of restriction enzyme. However, those methods are time-consuming, labor-intensive and expensive. To overcome these shortcomings, we developed an Exonuclease III based DNA cloning method that takes only 30 minutes with high cloning efficiency and significant economic advantage. Therefore, this method is suitable for large-scale gene cloning.
Cloning, Molecular ; methods ; DNA ; chemistry ; DNA Restriction Enzymes ; Exodeoxyribonucleases ; chemistry ; Genetic Vectors ; Polymerase Chain Reaction

DNA binding compounds were previously shown to bind to the right-handed DNA forms and hybrid B-Z forms in a highly cooperative manner and indicate that structural specificity plays a key role in a ligand binding to DNA. In this study, the modes of binding and structural specificity of agents to unusual DNA are examined by a variety of fluorescence techniques (intensity, polarization and quenching, etc.) to explore a reliable method to detect the association environment of ligands to deoxyoligonucleotides initially containing a B-Z junction between the left-handed Z-DNA and right-handed B-DNA. The results of fluorescence energy transfer measurement demonstrated that the ligand molecules bind to the allosterically converted DNA structures by intercalation. In the absence of high-resolution structural data, this fluorescence energy transfer measurement allowed reliable measures and infer the binding environment of ligands to the allosteric DNA structures.
Allosteric Regulation ; Circular Dichroism ; DNA/*chemistry/*metabolism ; Energy Transfer ; Ethidium/*metabolism ; Exodeoxyribonucleases/metabolism ; Ligands ; Motion ; Nucleic Acid Conformation ; Oligodeoxyribonucleotides/*metabolism

A novel exonuclease protection mediated PCR assay (EPM-PCR) to detect the interaction of protein and DNA at a dioxin-responsive enhancer (DRE) upstream of the CYP1A1 gene in rat hepatic cytosol was established. A double-stranded DNA fragment containing two binding sites was designed and incubated with the aryl hydrocarbon receptor (AhR) transformed by 2,3,7,8-tetrachlorodibenzo-p dioxin (TCDD) to generate TCDD: AhR: DNA complex which could protect receptor-binding DNA against exonuclease II (Exo III) digestion. With Exo III treatment, free DNAs were digested and receptor-bound DNAs remained that could be amplified by PCR. By agarose gel electrophoreses a clear band (285bp) was detected using TCDD-treated sample, while nothing with control samples. To detect transformed AhR-DRE complex, 2 fmol DNAs and 3 ug cytosol proteins were found to be sufficient in the experiment. Compared with gel retardation assay, this new method is more sensitive for monitoring the Ah receptor-enhancer interaction without radioactive pollution.
Binding Sites ; Cytochrome P-450 CYP1A1/*genetics ; Cytosol/metabolism ; DNA-Binding Proteins/chemistry ; Exodeoxyribonucleases/chemistry ; Liver/*metabolism ; Polymerase Chain Reaction ; Rats, Sprague-Dawley ; Receptors, Aryl Hydrocarbon/*chemistry ; Tetrachlorodibenzodioxin/*analogs & derivatives ; Tetrachlorodibenzodioxin/chemistry