We have identified hybrid plasmids carrying the melibiose operon of Escherichia coli in a colony bank of Clarke and Carbon (Tsuchiya, T., Ottina, K., Moriyama, Y., Newman, M., and Wilson, T. H. (1982) J. Biol. Chem. 257, 5125-5128). Using one of the plasmids as a starting material, the DNA fragments containing the melibiose operon were recloned in a vector pBR322. Restriction maps were prepared...

The binding of chromosomal protein HMG1 to a palindromic sequence that can form the cruciform structure in supercoiled DNA and the subsequent effect on the transcription of the sequence were examined with pBR322 and its derivative plasmids. The plasmid DNA under negative supercoiling showed a selective sensitivity to nuclease S1. HMG1 protected against the nuclease S1 digestion. The results of ...

Development of radioprotective agents has been a subject of intense research to ameliorate the aftermath of exposure to radiation exposure. The aim of the study was to determine the antioxidant and radioprotective potentials of the fruit extract of Oroxylum indicum (L.) Vent. Free radical scavenging activity of O. indicum fruit extracts was determined through DPPH and superoxide assays. Ascorbi...

Here we report the cloning and preliminary characterization of the Pst I restriction-modification system of Providencia stuartii 164. Transformants of Escherichia coli carrying the Pst I gene system inserted into the cloning vector pBR322 were selected on the basis of acquired resistance to bacteriophage lambda infection. Pst I endonuclease was detected in osmotic shock fluid from each of the r...

OBJECTIVE To investigate the effects of β-Elemene (β-ELE) on the proliferation, apoptosis, and topoisomerase I (TOPO I) and topoisomerase IIα (TOPO IIα) expression and activity of human hepatocarcinoma HepG-2 cells. METHODS After treatment with β-ELE, morphological alterations of HepG-2 cells were observed under an inverted microscope. Cell proliferation was assessed using an MTT assay, cell ...

We test here whether a class of deletions likely to result from errors during DNA replication arise preferentially during synthesis of either the leading or the lagging DNA strand. Deletions were obtained by reversion of particular insertion mutant alleles of the pBR322 amp gene. The alleles contain insertions of palindromic DNAs bracketed by 9-bp direct repeats of amp sequence; in addition, bp...

With the mutagenesis of specific, virulence-associated genes of Legionella pneumophila as the eventual goal, methods for gene transfer to these bacteria were developed. Following the observations of others that conjugative, broad-host-range plasmids could be transferred from Escherichia coli to L. pneumophila at low frequency, we constructed a small mobilizable vector, pTLP1, which carries oriV...

Genetic mapping studies had shown that the bacterial transposon Tn5 can insert into many sites in a gene, but that some sites are preferred. To begin understanding Tn5's insertion specificity at the molecular level, we selected transpositions of Tn5 from the Escherichia coli chromosome to the plasmid pBR322 and analyzed the resultant pBR322::Tn5 plasmids by restriction endonuclease digestion an...

A cloned 270-nucleotide fragment from the origin region of the M13 duplex replicative form DNA confers an M13-dependent replication mechanism upon the plasmid vector pBR322. This M13 insert permits M13 helper-dependent replication of the hybrid plasmid in polA cells which are unable to replicate the pBR322 replicon alone. Using in vitro techniques, we have constructed several plasmids containin...