Rapid purification of bacterial plasmids and coliphage M13 RF without CsCl centrifugation

Use of a transient expression assay for the optimization of direct gene transfer into tobacco mesophyll protoplasts by electroporation

Plasmid DNA was transfected into tobacco mesophyll protoplasts by electroporation. Transfection efficiency was estimated, using a transient expression assay based on the measurement of chloramphenicol transacetylase activity or by scoring colonies expressing resistance to paromomycin, an aminoglycoside related to kanamycin. Under conditions of cell survival superior to 50% after electroporation, transient expression signals and transformation efficiencies were found to be proportional. Factors affecting the efficiency of transformation were studied. A clear-cut optimum voltage (250-300 V/cm) was detected. Among various salts tested, potassium chloride was the best electrolyte. No improvement of electroporation efficiency was obtained by a heat-shock (45 degrees C/5 min) treatment prior to electroporation or by the presence of polyethylene glycol in the electroporation medium. The physiological state of plants used as the protoplast source significantly affected the transfection ability of the resulting protoplasts. These results are discussed and compared to previously published procedures.

An economical large scale procedure to purify E. coli amplifiable plasmids for DNA sequencing, in vitro transcription and in vitro mutagenesis

A reproducible and economical procedure for obtaining a large and quantitative yield of highly purified covalently closed circular plasmid DNA is described. The procedure departs in several ways from more commonly used methods. These are a) avoidance of the use of CsCl, ethidium bromide and ultracentrifuge, b) enrichment of the plasmid DNA by selective denaturation of chromosomal DNA with an alkaline-SDS solution, c) enrichment of covalently closed circular plasmid DNA by extraction with acid-phenol, and d) removal of small degraded RNA fragments by molecular sieve chromatography after digestion with RNase A. The plasmid DNA prepared by this new procedure is free of contaminants and has been used for DNA sequencing, in vitro transcription, transformation and in vitro mutagenesis.

Efficient DNA-mediated transfer of selectable genes and unselected sequences into differentiated and undifferentiated mouse melanoma clones

We have found that three phenotypically dissimilar mouse B16 melanoma subclones are competent recipients for DNA-mediated gene transfer. Two of these approach and a third, amelanotic clone B78H1, surpasses mouse LTK cells in frequencies of transferent colony formation after treatment with either of two codominantly selectable plasmid vectors, pSV2gpt or pGCcos3neo. Melanoma transferents incorporate both selectable plasmid-homologous sequences and substantial amounts of unselected donor DNA into their cellular DNAs. In addition they retain the distinctive states of differentiation characteristic of the untreated clones. Frequencies of pGCcos3neo-mediated transfer of neo gene-encoded antibiotic resistance into B78H1 can reach 10(-2) in response to treatment with as little as 15 ng plasmid/ml coprecipitate/dish. B78H1 cells readily give rise to "secondary" transferents for the neo gene after treatment with DNA from a "primary" B78H1 neo transferent. This gene transfer system has potential applications for study of regulation of melanoma and neural crest differentiation and malignancy.