SEARCH · PubMed Health

Results for “replicative form”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 235 records · Page 13Linked to original sources

PubMed1970

Intracellular development of bacteriophage phi-R. II. Fractionation of replicative form deoxyribonucleic acid associated with rapidly sedimenting host cell components.

When Escherichia coli is infected with bacteriophage phiR, parental deoxyribonucleic acid (the single- or double-stranded DNA containing the isotopic label of the infecting phage) becomes firmly attached to a cellular structure and can be isolated as a rapidly sedimenting component as described earlier for phiX174. If this component is centrifuged to equilibrium, two peaks of infective DNA are observed at densities of 1.30 and 1.15 g/ml. At low multiplicities of infection, (32)P-labeled parental DNA is found associated with only the cellular components in the dense band; as the multiplicities of infection are increased, the dense band becomes saturated and parental DNA molecules are then found at the light density as well. Actively replicating host DNA is found only in the dense band, whereas progeny DNA, which does not replicate semiconservatively, can become associated with cellular components in the light band. This fractionation of cellular components on the basis of their buoyant density separates primary sites of DNA replication associated with the dense band from nonfunctional binding sites in the light band.

Carbon Isotopes↗

PubMed1982

In vitro conversion of MVM parvovirus single-stranded DNA to the replicative form by DNA polymerase alpha from Ehrlich ascites tumour cells.

A partially purified preparation of DNA polymerase alpha, obtained from the cytosol of Ehrlich ascites tumour cells, has been found to catalyze the conversion of MVM parvovirus, SS DNA (5 kilobases) to RF in vitro. The reaction initiates at a natural 55 base pair hairpin which exists at the 3' terminus of MVM SS DNA. The SS leads to RF conversion is sensitive to aphidicolin, resistant to ddTTP and is promoted by purine ribonucleoside 5' triphosphates, a phenomenon which could not be explained simply by stabilization effects on the in vitro deoxynucleotide precursor pool. In the absence of rNTPs, nascent complementary strands frequently terminate prematurely at a preferred location, between 1300 and 1700 nucleotides from the initiating 3' hairpin terminus. This in vitro system, involving self-primed parvovirus DNA synthesis, provides a convenient assay for those components of the mammalian replicative DNA polymerase complex which are required for the elongation of nascent DNA chains.

Animals↗

PubMed1978

Isolation of circular viral and complementary strand DNA from bacteriophage f1 duplex replicative-form DNA.

A general method has been developed for the large scale isolation of intact, circular, single-stranded DNA molecules of each strand from supercoiled duplex DNA. The method involves the conversion of the supercoiled duplex DNA to singly nicked, relaxed duplex DNA; denaturation of the duplex DNA; separation of circular DNA molecules from linear DNA molecules; and separation of circular plus and minus strands. All separations involve zone sedimentation. No isopycnic gradient centrifugation is required. The last step in the purification, the separation of plus and minus strands, can be easily adapted for small scale analytical measurements of the amounts of plus and minus strand DNA.

Centrifugation, Zonal↗

PubMed1995

Detection of replicative form of HCV RNA in peripheral blood leukocytes and its clinical significance.

Nested RT-PCR, done by using degenerated primer pair, was used to detect hepatitis C virus RNA (HCV RNA) in serum, plasma, liver and peripheral blood mononuclear cells (PBMC) of 30 patients with acute and chronic posttransfusion hepatitis C and 7 asymptomatic anti-HCV positive subjects. The results showed that the percentages of both the plus and minus strands of HCV RNA in PBMC of the patients with chronic hepatitis C was significantly higher than that with acute hepatitis C and asymptomatic anti-HCV positive subjects (P < 0.05-0.001). In 17 patients who were subjected to biopsy, the positive rate of the both strands of HCV RNA in PBMC of the patients with AH was lower than that of CAH (P < 0.05). In serum and plasma of all 37 cases, the minus strand of HCV RNA was not detected. Both plus and minus strands in liver of one patient with AH were positive, but the minus strand in PBMC negative. In 6 patients with CAH whose both strands in liver were positive, both strands in PBMC in 5 patients were also found. The present data confirmed that PBMC of the patients with hepatitis C were infected by HCV and the longer the infection time, the bigger the possibility of PBMC infection by HCV. The patients with active liver disease (CAH) had higher positive rate of minus strands of HCV RNA in PBMC. The results suggested that HCV may not only infect PBMC but also replicate in PBMC, and that the occurrence of minus strand of HCV RNA is associated with activity of liver disease.

Adult↗

PubMed1995

[Detection of replicative form of HCV RNA in peripheral blood leukocytes and its clinical significance].

Nested RT-PCR, done by using degenerated primer pair, was used to detect hepatitis C virus RNA (HCV RNA) in serum, plasma, liver and peripheral blood leukocytes (PBLC) of 30 patients with acute and chronic posttransfusion hepatitis C and 7 asymptomatic anti-HCV positive subjects. The results showed that the percentage of positive HCV RNA in PBLC, including both the plus and minus strands, in patients with chronic hepatitis C was significantly higher than that in acute hepatitis C and asymptomatic anti-HCV positive subjects (P < 0.05-0.001). All the 7 asymptomatic anti-HCV positive subjects did not have detectable minus strand of HCV RNA in their PBLC, serum or plasma. In 17 patients who had liver histologic examination, the positive rate of both strands of HCV RNA in PBLC of acute hepatitis (AH) was lower than that of chronic active hepatitis (CAH) (P < 0.05). Both strands of HCV RNA were detected in the liver of one AH and 6 CAH patients. The present data confirmed that PBLC of patients with hepatitis C were indeed infected by HCV. The longer the infection time, the more the chance of PBLC being infected by HCV. Patients with active liver disease (CAH) had usually higher positive rate of minus strands of HCV RNA in PBLC. In the serum and plasma of all the 37 cases, minus strand of HCV RNA was not detected and the positive rate of the plus strand of HCV RNA in their serum and plasma was similar. Futhermore, the positive rate of both plus and minus strands of HCV RNA in PBLC of 30 patients with chronic hepatitis C was also similar. It is suggested that HCV not only may infect PBLC, but also replicate in PBLC and that the occurrence of minus strand of HCV RNA is associated with activity of liver disease.

Adult↗

PubMed1983

Site specific cleavage of phi X-174 replicative form DNA after modification by N-acetoxy-N-2-acetylaminofluorene.

Three kinds of structural disturbances were found in an 88 base pair (bp) fragment of phi X-174 DNA after exposure to N-acetoxy-N-2-acetylaminofluorene (N-Aco-AAF). (i) Frequent strand scissions at two specific guanine sites on the 5' 32P-end-labeled fragment were identified by base sequence analysis. Scissions at these two sites were induced at neutral pH and they were not increased by treatment with apurinic endonuclease. They are an immediate consequence of N-Aco-AAF action and are not primarily apurinic sites. (ii) Alkali treatment with 1 M piperidine at 90 degrees C induced strand scissions at every guanine, demonstrating adduct slices, depurination and strand scissions. (iii) Adducted DNA was sensitive to single-strand specific nuclease digestion, suggesting unwound DNA. These studies indicate the prediliction of N-Aco-AAF for certain DNA sites and they suggest three kinds of DNA modifications which can be expected after adduction by this carcinogen. Some of the sites may be premutational carcinogen-induced DNA structural modifications.

2-Acetylaminofluorene↗

PubMed1977

Electron microscopy analysis of the interaction between Escherichia coli DNA-dependent RNA polymerase and the replicative form of phage fd DNA. 2. Analysis of the dissociation kinetics.

The kinetics of dissociation of the fd DNA - RNA-polymerase complex has been analyzed. Heparin was added to a solution of the enzyme - DNA complex in order to trap free polymerases. At different times after, samples were taken and analyzed by electron microscopy to determine the mean number of enzymes bound per DNA molecule. Unexpectedly, the measured dissociation is not a first-order reaction. The apparent rate constant increases with heparin concentration in the range between 0.001 and 2 mg/ml. These results strongly suggest the existence of a direct transfer process of RNA polymerase to heparin, bypassing the rate-limiting step of dissociation of the enzyme - DNA complex to free enzyme. Theoretical analysis of the direct-transfer model shows that the rate constant of dissociation should level off at high heparin concentrations: measurements of the residual transcription activity show that this is the case. From these experiments, the equilibrium constant of the DNA - RNA-polymerase complex can be determined. The value K = 10(12) M-1 which is obtained solves a striking paradox which existed because measurements performed in other laboratories indicated K = 10(14) M-1, which is greater than the equilibrium constant of the lac-repressor - lac-operator complex (=10(13) M-1).

Coliphages↗

PubMed2001

Development of a strand-specific RT-PCR based assay to detect the replicative form of hepatitis C virus RNA.

The recent development of tagged RT-PCR and rTth RT-PCR has greatly improved strand-specific detection of hepatitis C virus (HCV) RNA but these assays are still prone to some false detection of the incorrect strand of RNA. In this study we aimed to address additional factors which contribute towards false detection of HCV RNA. Firstly the benefits of both tagged primers and the thermostable reverse transcriptase rTth during cDNA synthesis were combined and it was found that strand specificity was greatly improved without compromising sensitivity. The reliability of the assay was then optimised by addressing the following issues: control synthetic transcripts should be free of contaminating plasmid DNA, residual RT activity should be minimised in the presence of PCR primers and cDNA should be free of unincorporated tagged RT primer prior to PCR amplification. The alterations made to the assay eliminated completely false detection of the incorrect strand of RNA in the control assay whilst the correct strand was consistently detected at a cDNA dilution of 10(-3)-10(-4). Negative strand was not detected in RNA isolated from serum but was detected, at a ten-fold lower level than positive strand, in RNA isolated from liver tissue.

DNA Repair Enzymes↗

PubMed2001