Binding of polycyclic aromatic hydrocarbons to DNA of cells in culture: a rapid method for its analysis using hydroxylapatite column chromatography.

A rapid procedure to study the interaction of carcinogens with DNA in cultured cells has been developed. The cells, which are labeled with 7,12-[3H]dimethylbenz[a] anthracene ([3H]DMBA), are lysed with 0.24 M phosphate buffer (pH 6.8), 1% sodium dodecyl sulfate (SDS), 8 M urea and 0.01 M ethylenediamine-tetraacetate (EDTA) and sonicated. The cell lysates are fractionated on columns of hydroxylapatite. Proteins and RNA are removed with 8 M urea in 0.24 M phosphate buffer (pH 6.8). DMBA-bound DNA is eluted with 0.4 M phosphate buffer (pH 6.8). DMBA-DNA isolated by this procedure is virtually free from proteins and RNA. Thermal stability, ultraviolet spectra and the density of DNA is not altered by DMBA binding. The uptake of DMBA by mouse epidermal cells is rapid and the binding of DMBA to DNA is linear for the first 8 h of exposure. DMBA binds to DNA in all phases of the cell cycle. However, the highest binding occurs immediately following maximum DNA synthesis.     

Isolation OP DNA Prom Yeast by Chromatography on Hydroxyapatite

A simple procedure is described for isolation of purified non degraded total DNA from yeast cells. The procedure involves conversion of the cells into sphero-plasts by enzymatic treatment, lysis of the sphero-plasts in 8 M urea - 0.24 M sodium phosphate buffer -0.01 M EDTA (ethylendiamintetraacetic acid, sodium salt) - 1% SDS (sodium dodecyl sulphate), deproteiniza-tion of the lysate with chloroform-phenol and separation of the DNA from proteins, RNA and other contaminants by hydroxyapatite chromatography. The yield is about 90% of the DNA in the starting material (sphero-plasts).     

Rapid purification of plasmid DNAs by hydroxyapatite chromatography.

A method is described for the rapid preparation of plasmid DNAs of molecular weight up to 14 X 10(6). This method involves the chromatography, at room temperature, of bacterial cleared lysates on hydroxyapatite in the presence of high concentrations of phosphate and urea. All detectable protein and RNA contamination of plasmid DNA is removed by this procedure and the conformation of the plasmid DNA is unaffected. Less than 0.5% chromosomal DNA is present in the purified preparation and even this can be removed if necessary by a simple extention of the procedure to include a heat-denaturation step. The method is extremely rapid and amenable to large-scale plasmid preparation; 5 mg ColE1 DNA have been purified within 40 min. The yield of plasmid DNA is similar to that obtained with the conventional dye-centrifugation technique, however the purity is greater.     

猕猴(Macaca mulatta)肝5S核糖核蛋白体RNA的分离提纯

应用酚-去污剂和1摩尔/升NaCl抽提低分子量RNA,通过DEAE-葡聚糖A-50离子交换层析提纯后,经含有7摩尔/升尿素的10%聚丙烯酰胺凝胶垂直板电泳制备纯化猕猴肝5S核糖核蛋白体RNA是简易而行之有效的方法。制纯的5SrRNA经聚丙烯酰胺凝胶电泳鉴定呈现单一的一条区带。与大肠杆菌5SrRNA标准品具有相同的电泳迁移率。     

Large-scale isolation of plasmid DNA and purification of lambda phage DNA using hydroxylapatite chromatography

A rapid and relatively simple procedure for purifying large quantities of plasmid DNA is described. Plasmid thus purified contains no detectable chromosomal DNA and little RNA or protein. The procedure combines alkaline denaturation and hydroxylapatite chromatography and utilizes an improved method of separating DNA from RNA. It was observed that the phosphate concentrations at which previously bound DNA as well as RNA elute from hydroxylapatite changed markedly as a function of urea concentration. In the presence of urea concentrations higher than 4 M, the ranges of phosphate concentration over which DNA and RNA elute show no overlap. This permits efficient washing of hydroxylapatite-bound DNA under conditions which should remove all bound RNA. lambda Phage DNA is also easily eluted from hydroxylapatite under the conditions used.     

介绍一种简单高效的植物总RNA提取方法

在液氮中研磨小麦幼叶和不同发育时期的种子,经含0.1% SDS和0.1%十二烷基肌氨酸钠(LDS)的尿素缓冲液裂解后,醋酸钠和氯仿沉淀变性蛋白质,异丙醇沉淀核酸,溶解后经2.5mol/L LiCl沉淀总RNA,洗涤后就可得到高质量的总RNA,其OD260/OD280 为2.05~2.10,28S和18S RNA带清晰,叶片总RNA还可得到23S和16S RNA带,产率可达5mg RNA/10g材料。当使用含1% SDS和1% LDS的尿素缓冲液裂解材料时,则可用于DNA的分离提取,其分子大小可达50~100kb以上。 Abstract:Wheat leaf and seeds at different development stages had been squashed in liquid nitrogen,then lysised by urea buffer which contains 0.1% SDS and 0.1% LDS,denatured protein had been removed by NaAc and chloroform precipitation,total RNA was further purified by LiCl.The RNA we obtained had sharp bands of 28S and 18S after agarose gel electrophoresis,23S and 16S RNA bands can also be seen clearly in leaf RNA extract,the value of OD260/OD280 of RNA was 205~210.5mg RNA can been isolated from 10g leaf of wheat.This method can also been used in high molecular weight DNA isolation but the concentration of SDS and LDS must be increased to 1%.     

A modified method for the preparation of agarose.

A simple procedure for the preparation of agarose suitable for electrophoresis is developed in which anionic polysaccharides are removed by extracting the agar gel-granules with phosphate buffer (0.03 M, pH 6.8) containing urea (4 M), followed by electrophoresis in the same buffer system. Further, alkali treatment in the presence of sodium borohydride, eliminates electroendosmosis, giving essentially a neutral agarose, as judged by the electrophoretic behaviour of basic substances like crystal violet and cytochrome C. The purified agarose with yields 60-65%, has a sulphur content less than 0.1%, and forms rigid, transparent gels.     

Subcellular distribution and properties of poly(A)-containing RNA from cultured plant cells.

Cultured sycamore cells rapidly incorporate [3H]uridine or [32P]orthophosphate into rRNA precursors and polydisperse RNA. Mature rRNA accumulates only after a lag period of approximately 40 min. Fractionation of pulse-labelled cells and analysis of the RNA shows that after 30 min the rRNA precursors, together with some polydisperse RNA, are confined to the nucleus. In consequence radioactive polydisperse RNA can be isolated from polyribosomes in the complete absence of labelled rRNA. Approximately 40% of this RNA is retained by an oligo(dT)-cellulose column and by this criterion is judged to contain poly(A) sequences. A smaller proportion of nuclear polydisperse RNA also contains poly(A). The tendency for poly(A)-containing RNA to aggregate complicates molecular weight determinations. Denaturation of poly(A)-containing RNA in 8 M urea prior to gel electrophoresis produces a broad peak of RNA with an average Mr = 10(6). Analysis of the nucleotide composition of total cell poly(A)-containing RNA shows that it contains 41% AMP. Roughly 6% of this RNA is resistant to digestion by ribonuclease A and T1. AMP is the only nucleotide detectable in these fragments. From their mobility during electrophoresis in 8 M urea at 60 degrees C with 5.8-S, 5-S and tRNA as molecular weight markers it is concluded that the poly(A) regions contain an average of 160 nucleotides.     

A simple, efficient method for the separate isolation of RNA and DNA from the same cells.

A method for the isolation of total cytoplasmic RNA and high molecular weight DNA from the same cells is described. Cells are gently lysed with NP40 in the presence of vanadyl ribonucleoside complex and the nuclei pelleted by centrifugation. RNA is purified by phenol/CHCl3 extraction of the lysate supernatant followed by ethanol precipitation. Protein is removed from high molecular weight DNA by salt-precipitation after nuclei are digested with proteinase K in the presence of sodium dodecyl sulfate. High yields of clean, intact RNA and DNA are obtained. A major advantage of the method is that it can be scaled down to quantitatively extract RNA and DNA from as little as 1000 cells.     

Preparative elution of proteins from nitrocellulose membranes after separation by sodium dodecyl sulfate-polyacrylamide gel electrophoresis

Various conditions were analyzed and optimized for the preparative elution of proteins from nitrocellulose membranes after transfer from sodium dodecyl sulfate (SDS)-polyacrylamide gels. The efficiency of elution was best using pyridine or acetonitrile elution solvents, intermediate for buffer containing a mixture of sodium dodecyl sulfate, Triton X-100, and sodium deoxycholate, and negligible for buffers containing any single detergent or chaotropic salt, such as urea or guanidine hydrochloride. The efficiency of elution with any solvent also depended on the molecular weight of the proteins, smaller proteins being more easily removed from membranes. As a general procedure, proteins may be eluted from nitrocellulose membranes by incubation with either 40% acetonitrile or 50% pyridine in 0.1 M ammonium acetate, pH 8.9, for 1-3 h at 5-37 degrees C. The recommended procedures for protein elution appear to offer a rapid, simple, and efficient means of recovering proteins from complex mixtures after separation by SDS-PAGE and transfer to nitrocellulose membranes.     

Rapid purification of covalently closed circular DNAs of bacterial plasmids and animal tumor viruses

A rapid and simple purification of covalently closed circular (supercoiled) DNA from both bacterial clones (plasmids) and African green monkey cells (SV40) is presented. The method involves immediate treatment of lysed cells with sodium hydroxide, followed by neutralization and phenol extraction in high salt. After the extraction mixture is centrifuged, supercoiled DNA is found in the aqueous phase, the noncovalently closed DNA molecules form a white precipitate at the interphase, and proteins pellet. Contaminating RNA is eliminated from the aqueous phase by RNAse treatment and precipitation of the supercoiled DNA with polyethylene glycol. Residual polyethylene glycol is removed from the resuspended DNA by chloroform extraction. The purified supercoiled DNA is compatible with restriction enzymes, and is efficient at transforming both _χ1776 and HB101 bacterial hosts. Centrifugation in ethidium bromide-cesium chloride or sucrose gradients is not necessary. The method is virtually independent of the molecular size and gives good yields of supercoiled DNA. The technique is applicable to large-scale preparations and as a rapid “screening” procedure in which 20 to 30 samples can be easily purified within 5 to 6 h.     

Rescue of chromosomal T-antigen sequences onto extrachromosomally replicating, defective simian virus 40 DNA by homologous recombination.

Recombination between chromosomal and extrachromosomal DNA sequences was analyzed by investigation of the recombinational rescue of a 1,018-base-pair (bp) segment of the T-antigen gene of simian virus 40 from the chromosome of monkey COS cells to two different, extrachromosomally replicating, simian virus 40 DNA molecules lacking this 1,018-bp sequence. The ratio of rescued to unrecombined virus was as high as 10(-3). The rescued molecules, detected optimally 5 to 9 days after transfection of COS cells, had completely recovered the 1,018-bp DNA segment from the chromosome. The recombination event is proposed to occur either by double reciprocal recombination or by gene conversion between the chromosomal T-antigen gene and the extrachromosomal molecules missing the 1,018-bp sequence.     

Isolation and physico-chemical properties of homogenous nuclease from Serratia marcescens

A simplified procedure for purification of nuclease from Serratia marcescens, including chromatography on DEAE- and phosphocellulose in a stationary regime has been developed. The method described results in a physically homogenous enzyme, which does not contain phosphatase, phosphodiesterase or proteinase admixtures. The molecular weight of the enzyme as determined by polyacrylamide gel electrophoresis is 33 000 +/- 10%. p-Chloromercurybenzoate (10(-2) M) completely inactivates the enzyme, while beta-mercaptoethanol (0,64 M) in the presence of 2 M urea causes only partial inactivation of the enzyme. Urea (4 or 7 M), when added to the reaction mixture, increases the enzyme activity 2,2-, 1,7- and 1,4-fold as compared to native, denaturated DNA and RNA, respectively.     

Cells of pea (Pisum sativum) that differentiate from G2 phase have extrachromosomal DNA.

Velocity sedimentation in an alkaline sucrose gradient of newly replicated chromosomal DNA revealed the presence of extrachromosomal DNA that was not replicated by differentiating cells in the elongation zone. The extrachromosomal DNA had a number average molecular weight of 12 X 10(6) to 15 X 10(6) and a weight average molecular weight of 25 X 10(6), corresponding to about 26 X 10(6) and 50 X 10(6) daltons, respectively, of double-stranded DNA. The molecules were stable, lasting at least 72 h after being formed. Concurrent measurements by velocity sedimentation, autoradiography, and cytophotometry of isolated nuclei indicated that the extrachromosomal molecules were associated with root-tip cells that stopped dividing and differentiated from G2 phase but not with those that stopped dividing and differentiated from G1 phase.     

Enhanced resolution of circular and linear molecular forms of viroid and viroid-like RNA by electrophoresis in a discontinuous-pH system

A discontinuous-pH polyacrylamide gel electrophoresis system is described. An increase in the pH differential between the gel and the running buffer enhances the separation of low molecular weight circular and linear RNA molecules. Highly purified preparations of the circular form of viroids can be obtained with this procedure. Since all the linear RNAs of similar molecular weight migrate with the front, a relatively clean background can be obtained even when crude extracts are used. This facilitates an improved separation and identification of similarly sized viroid-like RNAs. The conditions of electrophoresis in low salt and 8 M urea also permit the effective transfer of RNA molecules directly to nylon-based membranes without any additional denaturation treatment.     

Simian virus 40-specific polypeptides in AD2+ ND1- and Ad2+ ND4-infected cells.

A comparison of the proteins synthesized in human cells at late times after infection with adenovirus (Ad2) and with the adeno-simian virus 40 (SV40) hybrid viruses revealed polypeptides of 30,000 and 92,000 molecular weight specific for the hybrid viruses Ad2+ND1 and Ad2+ND4, respectively. Cell-free translation of SV40-specific mRNA, prepared from these cells by hybridization of total cytoplasmic RNA to SV40 DNA, showed that the mRNA's specifying these two polypeptides were at least partially encoded by the SV40 portion of the hybrid viruses. Cell-free translation of SV40-specific mRNA prepared from monkey cells infected with SV40 produced polypeptides of 40,000, 43,000, 48,500, and 92,000 molecular weight. The SV40 and Ad2+ND4 92,000-molecular-weight polypeptides made in vitro were very similar in electrophoretic mobility in sodium dodecyl sulfate-polyacrylamide gels to the polypeptide precipitated by Tegtmeyer (1974) with SV40 anti-T serum.     

Purification, Characterization, and Comparison of the DNA Polymerases from Two Primate RNA Tumor Viruses

The DNA polymerase from the Mason-Pfizer monkey virus (M-PMV), an RNA tumor virus not typical type-C or type-B, has been purified a thousand-fold over the original crude viral suspension. This purified enzyme is compared to a similarly purified DNA polymerase from the primate woolly monkey virus, a type-C virus. The two enzymes have similar template specificities but differ in their requirements for optimum activity. Both DNA polymerases have a pH optimum of 7.3 in Tris buffer. M-PMV enzyme has maximum activity with 5 mM Mg(2+) and 40 mM potassium chloride, whereas the woolly monkey virus optima are 100 mM potassium chloride with 0.8 mM Mn(2+). The apparent molecular weight of the M-PMV enzyme is approximately 110,000, whereas the woolly monkey virus polymerase is approximately 70,000. The biochemical properties of these two enzymes were also compared to a similarly purified enzyme from a type-C virus from a lower mammal (Rauscher murine leukemia virus). The results show that more similarity exists between the DNA polymerases from viruses of the same type (type-C), than between the polymerases from viruses of different types but from closely related species.     

Isolation and Characterization of the Fertility Factor P of Vibrio cholerae

Vibrio cholerae strains with the transmissible fertility factor P contained a supercoiled circular deoxyribonucleic acid (DNA) component amounting to between 2 and 6% of the total DNA obtained from the cells. Such a component was not observed in V. cholerae strains lacking the fertility factor. This supercoiled circular DNA was isolated from P(+) cells, and the molecular weight was determined by sedimentation velocity experiments and electron microscopy to be approximately 80 million daltons. These supercoiled circular DNA molecules, which have a guanine plus cytosine (G + C) composition of 42%, were concluded to be the extrachromosomal P factor. It was calculated that there is approximately one copy of the P factor per chromosome. A small amount of supercoiled circular DNA was occasionally isolated from the P(-) strains of V. cholerae. The function of this component, which has a molecular weight of 40 million daltons, is not known. The molecules found in the P(-) strains were readily distinguished from the P(+) circular molecules by their smaller molecular weight and different G + C composition.     

A procedure for purifying jack bean urease for clinical use

Urease with a purity meeting the requirements of analytical use was purified from jack bean meal through steps consisting of 20% acetone extraction, heat treatment, acid precipitation, and lyophilization. For extraction of urease, one part of bean meal was mixed with 5 parts of 20% acetone containing 1 mM EDTA and 1 mM 2-mercaptoethanol, and stirred at 20 degrees C for 5 min. Milky substances in the extract were removed by heat treatment. Urease in the clear yellow supernatant was precipitated by adjusting the pH of the solution to 5.4 with citric acid. The acid precipitated urease was neutralized by dissolving in 0.015 M phosphate buffer, pH 8.5 (final pH 6.8 to 7.0) and then lyophilized. By this procedure, the purity of the enzyme was increase 14.7 fold, the recovery of activity was 63%, and the yield was 6.75 g from 1 kg of bean seeds. The specific activity of the preparation was 411 units/mg protein (240 units/mg solid), and the free ammonia content was less than 0.01 microgram per unit. Some other proteins were present in the urease preparation as examined by gel filtration and gradient polyacrylamide gel electrophoresis. The molecular weight of the enzyme estimated by gel filtration was 480,000. However, two urease activity bands with molecular weight of 230,000 and 480,000 were observed in the polyacrylamide gel electrophoregram. From the result of determination of blood urea nitrogen (BUN), this simple purification procedure could be used for practical preparation of urease from jack bean meal for clinical analysis.     

Deoxyribonucleic Acid Replication in Simian Virus 40-Infected Cells: III. Comparison of Simian Virus 40 Lytic Infection in Three Different Monkey Kidney Cell Lines

A comparative study of simian virus 40 (SV40) lytic infection in three different monkey cell lines is described. The results demonstrate that viral deoxyribonucleic acid (DNA) synthesis and infectious virus production begin some 10 to 20 hr earlier in CV-1 cells and primary African green monkey kidney (AGMK) cells than in BSC-1 cells. Induction of cellular DNA synthesis by SV40 was observed in CV-1 and AGMK cells but not with BSC-1 cells. Excision of large molecular weight cellular DNA to smaller fragments was easily detectable late in infection of AGMK cells. Little or no excision was observed at comparable times after infection of CV-1 and BSC-1 cells. The different kinds of responses of these three monkey cell lines during SV40 lytic infection suggest the involvement of cellular functions in the virus-directed induction of cellular DNA synthesis and the excision of this DNA from the genome.