SEARCH · PubMed Health

Results for “nucleoprotein complex”

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 19 recordsLinked to original sources

PubMed1979

Association of simian virus 40 T antigen with simian virus 40 nucleoprotein complexes.

Viral nucleoprotein complexes were extracted from the nuclei of simian virus 40 (SV40)-infected TC7 cells by low-salt treatment in the absence of detergent, followed by sedimentation on neutral sucrose gradients. Two forms of SV40 nucleoprotein complexes, those containing SV40 replicative intermediate DNA and those containing SV40 (I) DNA, were separated from one another and were found to have sedimentation values of 125 and 93S, respectively. [(35)S]methioninelabeled proteins in the nucleoprotein complexes were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. In addition to VP1, VP3, and histones, a protein with a molecular weight of 100,000 (100K) is present in the nucleoprotein complexes containing SV40 (I) DNA. The 100K protein was confirmed as SV40 100K T antigen, both by immunoprecipitation with SV40 anti-T serum and by tryptic peptide mapping. The 100K T antigen is predominantly associated with the SV40 (I) DNA-containing complexes. The 17K T antigen, however, is not associated with the SV40 (I) DNA-containing nucleoprotein complexes. The functional significance of the SV40 100K T antigen in the SV40 (I) DNA-containing nucleoprotein complexes was examined by immunoprecipitation of complexes from tsA58-infected TC7 cells. The 100K T antigen is present in nucleoprotein complexes extracted from cells grown at the permissive temperature but is clearly absent from complexes extracted from cells grown at the permissive temperature and shifted up to the nonpermissive temperature for 1 h before extraction, suggesting that the association of the 100K T antigen with the SV40 nucleoprotein complexes is involved in the initiation of SV40 DNA synthesis.

Antigens, Neoplasm↗

PubMed1979

Effect of azacytidine on Simian Virus 40 nucleoprotein complexes.

Simian virus 40 nucleoprotein complexes synthesized in the presence of 5-azacytidine showed small differences in sedimentation rate on neutral sucrose and buoyant density in metrizamide and cesium chloride. Simian virus 40 deoxyribonucleic acid (DNA) I, isolated from the nucleoprotein complexes of drug-treated cultures, was found to band at a higher buoyant density and therefore had a decreased ability to bind ethidium bromide. The data indicated that these molecules were deficient in superhelical turns. Treatment with 5-azacytidine was shown to inhibit protein synthesis, which preceded the inhibition of DNA synthesis. Under the same conditions, protein synthesis was inhibited to a greater degree and occurred much faster than inhibition of DNA syntheses. Upon removal of the drug, resumption of protein and DNA synthesis occurred slowly. It is concluded that the inhibition of simian virus 40 DNA synthesis and the conformational alterations in DNA I isolated from nucleoprotein complexes result from the inhibition of protein synthesis.

Azacitidine↗

PubMed1978

DNA polymerase alpha is associated with replicating SV40 nucleoprotein complexes.

Simian virus 40 (SV40) nucleoprotein complexes were extracted from nuclei of infected monkey cells and fractionated on neutral sucrose density gradients. Complexes which contained replicating SV40 DNA (95S) separated well from those containing closed circular supercoiled viral DNA (75S). DNA polymerase activity was associated with the replicating nucleoprotein complexes but not with the slower sedimenting complexes. This DNA polymerase activity coprecipitated with the nucleoprotein complexes in the presence of MgCl2 and remained associated with the 95S complexes. This DNA polymerase activity has been identified as primarily DNA polymerase alpha on the basis of its sedimentation behavior, optimum salt concentration, and sensitivity to N-ethylmaleimide. DNA polymerase gamma activity was also detected in the complexes, but DNA polymerase beta was not associated with the complexes.

Cell Line↗

PubMed1978

Interaction of the DNA untwisting enzyme with the SV40 nucleoprotein complex.

The SV40 nucleoprotein complex which was isolated from infected CV-1 cells did not possess an active DNA untwisting enzyme. The superhelix density of the DNA in the chromatin complex was unchanged after treatment with purified rat liver DNA untwisting enzyme. However, in the presence of ethidium bromide (1 microgram/ml) the superhelix density was changed. Moreover, the nicked intermediate in the DNA untwisting reaction could be detected using the chromatin DNA as a substrate. These results show that the DNA in the SV40 chromatin which is accessible to the DNA untwisting enzyme is under no topological strain.

Chromatin↗

PubMed1979

Histone modifications in simian virus 40 and in nucleoprotein complexes containing supercoiled viral DNA.

Simian virus (SV40) nucleoprotein complexes containing circular supercoiled viral DNA were extracted from infected cells and purified by differential centrifugation. The protein content of these complexes was compared by electrophoresis on 15% acrylamide gels with the protein content of purified SV40 virions and with histones from virus-infected cells. The electrophoretic patterns of histones from each of the sources revealed several major differences. SV40 virions contained histones H3, H2B, H2A, and H4 but not H1. Nucleoprotein complexes and host cells contained all five major histone groups. Relative to cellular histones, virion and nucleoprotein complex histones were enriched 15 to 40% in histones H3 and H4. In addition to the major classes of histones, several subfractions of histones H1, H3, and H4 were observed in acrylamide gels of proteins from SV40 virions and viral nucleoprotein complexes. Acetate labeling experiments indicated that each subfraction of histones H3 and H4 had a different level of acetylation. The histones from SV40 virions and nucleoprotein complexes were acetylated to significantly higher levels than those of infected host cells. No apparent differences in phosphorylation of the major histone groups were observed.

Acetylation↗

PubMed1976

In vitro replication of simian virus 40 DNA in a nucleoprotein complex.

A simian virus 40 (SV40) nucleoprotein complex, extracted from nuclei isolated from a monkey cell line infected with SV40, continued DNA replication in the presence of a nuclear extract, cytosol, ATP, and ATP-regenerating system, and the four deoxyribonucleoside triphosphates. The DNA products of replication were also found as nucleoprotein complexes. Forty percent of the replicating viral DNA, labeled in vivo, was converted into covalently closed, superhelical DNA during incubation in vitro. Although the remaining labeled DNA was not converted into mature viral DNA, it was elongated to its full genome length. Failure to terminate replication successfully was not caused by endonuclease activity, since covalently closed DNA, labeled in vivo, was not damaged during incubation in vitro. When [alpha-32P]dATP was present during the incubation, the label appeared first in replicating DNA and later in mature DNA; no unusual products were labeled in vitro. The covalently closed SV40 DNA made in vitro had the same superhelical density as viral DNA made in vivo. These data demonstrate that viral nucleoprotein complexes ("minichromosomes") are able to continue DNA replication outside of the nucleus.

Cell Line↗

PubMed1978

Comparison of nuclease digestion of polyoma virus nucleoprotein complex and mouse chromatin.

We digested polyoma virus nucleoprotein complex, isolated from disrupted virions, with micrococcal nuclease and DNase I. The results were compared with digestions of chromatin from mouse nuclei. The nucleosome "core" structures were similar, but the spacing of the nucleosomes in the isolated polymoma nucleoprotein complexes was irregular, whereas in mouse chromatin it was regular. The average nucleosome repeat length in each case was 190 to 200 base pairs. This figure suggests that, unless there are substantial stretches of free DNA, the polyoma nucleoprotein complex contains about 26 nucleosomes. The commonly used method of preparing the nucleoprotein complex by disruption of virions at pH 10.2 may lead to significant damage to the structure. Such damage may be more clearly revealed by the susceptibility of the DNA to nuclease digestion than by the usual criteria of sedimentation velocity and buoyant density.

Animals↗

PubMed1979

Intracellular forms of simian virus 40 nucleoprotein complexes. I. Methods of isolation and characterization in CV-1 cells.

A new method was developed for isolation of intracellular forms of simian virus 40 (SV40) nucleoprotein complexes from SV40-infected CV-1 cells late in the infectious cycle. In contrast to the Triton extraction method, which yields only a 60-70S complex, this new procedure yielded three forms of SV40 nucleoprotein complexes: complex I, complex II, and the nature virion (V). The three nucleoprotein complexes differed in physical as well as biochemical properties. Complex I, which is only a small portion of the total SV42 nucleoprotein complexes late during infection, was active in synthesizing both SV40-specific DNA and RNA. Pulse-labeling experiments suggest the following metabolic pathway: I leads to II leads to V. Conversion of complex I to II occurred shortly after the completion of SV40 DNA replication and resulted in the inactivation of the biosynthetic activities of I.

Animals↗

PubMed1975

[Dyserythropoietic anemia, type I: ineffective erythropoiesis due to disorders in the DNA-nucleoprotein complex].

The relative DNA, RNA histone and hemoglobin contents and 3H-thymidine incorporation in vitro were determined sequentially in individual erythroblasts of type I dyserythropoietic anemia. The histone/DNA ratio was increased due to a rise in histone extinction, indicating a pathological DNA-nucleoprotein complex. In addition, the erythroblasts displayed an increase in DNA content exceeding tetraploid values, a loss of DNA-synthesis activity at immature stages with low hemoglobin content, and a reduction of RNA. These variations were assumed to be caused by the preceding and primary impairment of the DNA-nucleoprotein complex.

Adult↗

PubMed1975

DNA replication in SV40-infected cells. XI. The properties of SV40 DNA and nucleoprotein complex synthesized in the presence of cycloheximide.

Cycloheximide inhibits simian virus 40 (SV40) DNA synthesis in productively infected African green monkey kidney cells. The residual viral DNA synthesized in the presence of this drug is deficient in superhelical turns as measured by band sedimentation in the presence of several concentrations of ethidium bromide. The superhelical density of SV40 DNA synthesized in the presence of cycloheximide is about one half that of viral DNA produced in the absence of this drug. Ribonuclease H and alkali treatment were employed to determine if ribonucleotides could be detected in closed circular SV40 DNA synthesized in the presence of cycloheximide. While both these approaches detected ribonucleotides in mitochondrial DNA, no identification of ribonucleotides in SV40 DNA synthesized in the presence of cycloheximide was found. The SV40 nucleoprotein complex synthesized in the presence of cycloheximide has a slower sedimentation rate (35S) and a higher bouyant density (1.54 g/cm3) than the complex made in the absence of this drug (50S; 1.47 g/cm3). The protein:DNA ratio of the SV40 nucleoprotein complex is normally about 0.9. This ratio is reduced to about 0.6 when the complex is synthesized in the presence of cycloheximide.

Cell Line↗

PubMed1975

Formation of nucleoprotein complexes between polyoma empty capsides and DNA.

Purified polyoma empty capsids and polyoma type I DNA interact in a cell-free system to form nucleoprotein complexes. Complexes that consist of one, two, three, and four empty capsids per DNA molecule have been detected. Polyoma virions or capsomers do not react with added DNA to form such complexes.

Arginine↗

PubMed1978

Presence of RNA in the nucleoprotein complex spontaneously released by human lymphocytes and frog auricles in culture.

Cell systems as different as normal human blood lymphocytes and frog auricles release spontaneously a nucleoprotein complex in their culture medium. This release seems to be an active mechanism that is unrelated to cell death. The presence of RNA in this complex is demonstrated. The amount of extracellular RNA is regulated by the same homeostatic mechanism that has previously been shown to govern DNA release in the same cell systems. This extracellular RNA is linked by hydrogen bonds to the extracellular DNA and cannot be extracted by a usual phenol procedure, due perhaps to the presence of a glycoprotein. Further purifications by chloroform, sodium perchlorate, and hydroxyapatite are necessary to obtain an RNA molecule that is acid precipitable, RNase and KOH sensitive, and orcinol positive. The extracellular RNA sediments between 2.5 and 4S and is not a transfer RNA. It is more highly methylated than the 28S, 18S, and 4 to 5S cellular RNA. It activates DNA synthesis in vitro.

Animals↗

PubMed1992

The cAMP-CRP/CytR nucleoprotein complex in Escherichia coli: two pairs of closely linked binding sites for the cAMP-CRP activator complex are involved in combinatorial regulation of the cdd promoter.

Transcription initiation at CytR regulated promoters in Escherichia coli is controlled by a combinatorial regulatory system in which the cAMP receptor protein (CRP) functions as both an activator and a co-repressor. By combining genetic studies and footprinting analyses, we demonstrate that regulated expression of the CytR controlled cdd promoter requires three CRP-binding sites: a high affinity site (CRP-1) and two overlapping low affinity sites (CRP-2 and CRP-3) centred at positions -41, -91 and -93, respectively. In the absence of CytR, cAMP-CRP interacts at one set of sites (CRP-1 and CRP-2) and both of these binding sites are required for full promoter activation. In the presence of CytR, however, the two regulators bind cooperatively to cddP forming a nucleoprotein complex in which cAMP-CRP binds to CRP-1 and CRP-3 and CytR occupies the sequence between these sites. Thus, association of the two regulators involves a repositioning of the cAMP-CRP complex. Moreover, mutant cdd promoters in which CRP-2 and CRP-3 have been deleted are partially regulated by CytR, and cAMP-CRP and CytR still bind cooperatively to these promoters. These findings provide clues to an understanding of how cAMP-CRP and CytR interact at a structurally diverse set of promoters.

Bacterial Proteins↗

PubMed1977

Cell-free translation of RNA synthesized in vitro by a transcribing nucleoprotein complex prepared from purified vesicular stomatitis virus.

The RNA species synthesized in vitro by a transcribing nucleoprotein (TNP) complex of vesicular stomatitis virus (VSV) were translated with high efficiency in a fractionated cell-free system derived from reticulocytes. The use of TNP complexes isolated from VSV Indiana, VSV New Jersey, and Chandipura viruses showed that in each case the predominant polypeptides synthesized had electrophoretic mobilities identical to their virion N, NS, and M polypeptides in proportions reflecting those found in infected cells rather than purified virions. A minor polypeptide corresponding to unglycosylated polypeptide G was also observed, but the in vitro synthesis of polypeptide L was not detected. The addition of RNase inhibitor to transcription mixtures markedly increased the rate of RNA synthesis. Furthermore, the messenger activity of the RNA was significantly enhanced. The inclusion of S-adenosyl L-methionine during transcription substantially increased the messenger activity of the product RNA, suggesting a requirement for methylation. Fractionation by oligodeoxythymidylic acid-cellulose chromatography revealed that the RNA required a polyadnylic acid tract for messenger activity.

Cell-Free System↗

PubMed1978