The oriJ-based plasmids contain the origin of DNA replication from the cryptic Rac prophage, present in the chromosomes of most Escherichia coli K-12 strains. The organization of the oriJ replication region resembles ...
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The oriJ-based plasmids contain the origin of DNA replication from the cryptic Rac prophage, present in the chromosomes of most Escherichia coli K-12 strains. The organization of the oriJ replication region resembles that of the bacteriophage lambda, although sequence similarity is small. Here we investigated the regulation of replication of the oriJ-based plasmid in E. coli relA(+) and relA(-) hosts during amino acid starvation and limitation. i.e., during the stringent and relaxed responses. We found that, contrary to plasmids derived from phage lambda, replication of the oriJ-based plasmid proceeds efficiently during both stringent and relaxed responses. On the other hand, density shift experiments and measurement of the stability of a putative replication initiator protein (thr lambda O protein homologue) suggest that this replication may be carried out by the heritable replication complex, as previously demonstrated for lambda plasmids. We demonstrate that contrary to bacteriophage lambda p(R) promoter, an analogous promoter from the oriJ region is activated rather than inhibited at increased ppGpp levels. We propose that various responses of these promoters (p(R) and p(R).(R,JC), which are necessary for transcriptional activation of ori lambda and perhaps oriJ, respectively) to ppGpp are responsible for differences in the replication regulation between ori lambda- and oriJ-based plasmids during the stringent response. (C) 2000 Academic Press.
A cryptic plasmid designated pSBO2 (3582 bp) was isolated from Streptococcus bovis JB1. The pSBO2 contained putative sites for a double-strand origin (dso), a small transcriptional repressor protein (Cop), countertran...
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A cryptic plasmid designated pSBO2 (3582 bp) was isolated from Streptococcus bovis JB1. The pSBO2 contained putative sites for a double-strand origin (dso), a small transcriptional repressor protein (Cop), countertranscribed RNAs (ctRNAs), and a replication protein (Rep), which were similar to those from pMV158 and pLS1, which were isolated from S. agalactiae, and pWVO1, isolated from Lactococcus lactis. The putative single-strand origin (sso) of pSBO2 was similar to pER341 and pST1, which were isolated from S. thermophilus. Recombinant plasmid designated pSBE2 was constructed to bind pECM184 vector and the DNA fragment containing sso, dso, Cop, ctRNAs, and Rep of pSBO2. When pSBE2 was introduced into S. bovis 12-U-1 and no8, the plasmids in the transformants had deleted the 160-bp fragment between sso and ciao. This plasmid, designated pSBE2A, was capable of transforming Escherichia coli and S. bovis strains 12-U-1 and no8 on high frequency;therefore, pSBE2A is an effective shuttle vector.
A two-step protocol has been developed for isolation of plasmids from recombinant mycobacteria via Escherichia coli. First either mycobacterial primary transformants or propagated cultures were lysed in a mini-bead be...
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A two-step protocol has been developed for isolation of plasmids from recombinant mycobacteria via Escherichia coli. First either mycobacterial primary transformants or propagated cultures were lysed in a mini-bead beater using zirconia beads and the lysate thus obtained was used to transform E. coli recA mutant cells. Secondly, plasmid DNA was isolated from recombinant E. coli cells and analysed. Bead beating times of 2 min for Mycobacterium smegmatis, a rapid grower, and 4 min for M. bovis BCG, a slow grower, were found to be optimal for recovery of plasmid DNA. This protocol was also amenable to other mycobacterial species such as M. avium, M. fortuitum and M. tuberculosis H37Ra. Plasmid recovery from the recombinant M. bovis BCG using this protocol is approximately 300-fold higher than that reported for the electroduction method.
The yeast linear plasmid pCLU1, derived from pGKL1, has terminal proteins (TPs) covalently attached at the 5' ends of inverted terminal repeats (ITRs) and replicates in the cytoplasm, presumably using the TP as a ...
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The yeast linear plasmid pCLU1, derived from pGKL1, has terminal proteins (TPs) covalently attached at the 5' ends of inverted terminal repeats (ITRs) and replicates in the cytoplasm, presumably using the TP as a primer for DNA synthesis. In Saccharomyces cerevisiae, under certain conditions, pCLU1 migrated into the nucleus and replicated in either linear or circular form. The linear-form plasmid lacked TPs;instead it carried host-telomere repeats at the ITR ends. The present study showed that (1) the added telomere was primarily composed of the repeated tracts of TGTGTGGGT-GTGG, which was complementary to the RNA template of yeast telomerase, (2) the telomeric addition occurred at the very end of the ITRs, and (3) the sequence composition of the added telomeres was diverse among individual plasmids, but symmetrically identical at both ends of each plasmid. A similar mode of telomere addition was also observed in cells defective in the RAD52 gene. (C) 2000 Academic Press.
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