Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The PRL gene is expressed at a high basal level in rat pituitary tumor GH3 cells, and this basal level enhancement of PRL gene expression is maintained through a Ca2+-calmodulin-dependent mechanism. We have now examined whether the enzyme, DNA topoisomerase II, which has been shown to be phosphorylated by a Ca2+-calmodulin-dependent protein kinase, plays a role in the Ca2+-calmodulin-dependent basal level enhancement of PRL gene expression. The topoisomerase II inhibitor, novobiocin, at concentrations in the range of 35-140 microM, effectively blocked the ability of Ca2+ to increase PRL mRNA levels. Examination of the effects of novobiocin on the levels of protein synthesis, glucose-regulated protein (GRP) 78 mRNA, histone 3 mRNA, and 18S ribosomal RNA indicated that the drug selectivity inhibited PRL gene expression. Two other topoisomerase II inhibitors, m-AMSA and VM26, also diminished the Ca2+-induced levels of PRL mRNA at concentrations (100-400 nM) that did not lower total mRNA levels. We then examined whether topoisomerase II interacted nonrandomly with DNA from the 5' transcribed and 5'-flanking region of the rat PRL gene by in vitro mapping of topoisomerase II DNA cleavage sites. In initial assays with a 10.5 kilobase (kb) PRL genomic DNA fragment containing 3.5 kb of 5'-transcribed DNA and 7 kb of 5'-flanking DNA, we detected 4 major cleavage sites in the following regions: site 1, +1500 to +1600; site 2, +1 to -100; site 3, -1200 to -1300; and site 4, -2900 to -3000.(ABSTRACT TRUNCATED AT 250 WORDS)
Mol Endocrinol 1988 Jan
PMID:Evidence for a role of topoisomerase II in the Ca2+-dependent basal level expression of the rat prolactin gene. 284 May 67

The budding yeast Saccharomyces cerevisiae and the fission yeast Schizosaccharomyces pombe are both sensitive to camptothecin, an inhibitor of DNA topoisomerase I. An S. cerevisiae DNA repair mutant, rad52, is hypersensitive to the drug. In both species, topoisomerase I mutants totally lacking the enzyme are completely resistant to the drug. A strain with a mutation leading to a temperature-sensitive topoisomerase I exhibits temperature dependence in its in vivo response to camptothecin. A strain carrying a plasmid that overproduces topoisomerase I is hypersensitive to the drug. The rad52 mutant is killed by overproduction of the enzyme, even in the absence of the drug. The response of several of these strains to camptothecin analogs, to DNA topoisomerase II inhibitors, and to other drugs is reported. The cytotoxic effects of camptothecin are discussed in terms of the drug extending the lifetime of a topoisomerase I-DNA covalent intermediate, which is recognized as DNA damage by a DNA repair system.
Mol Pharmacol 1988 Dec
PMID:Evidence that DNA topoisomerase I is necessary for the cytotoxic effects of camptothecin. 284 43

Soluble extracts of Escherichia coli capable of carrying out replication of the mini-RK2 derivative pCT461 have been prepared from cells carrying this plasmid or from plasmid-free bacteria. The latter are dependent upon exogenously added plasmid-encoded replication protein (TrfA) and require additional DnaA protein for optimum activity. This dependence upon DnaA was confirmed by the failure of DnaA-deficient cell extracts to support replication of pCT461 in the absence of added DnaA protein. Replication is unidirectional and begins at or near oriV, the vegetative replication origin of RK2. DNase I protection studies with purified TrfA indicate that this protein acts by binding to short (17 base-pairs) directly repeated DNA sequences present in oriV. The in vitro replication is resistant to rifampicin but can be abolished by antibodies against DnaG protein (E. coli primase) or DnaB protein (helicase) and by DNA gyrase inhibitors. Inhibition by arabinosyl-CTP suggests that DNA polymerase III is responsible for elongation of nascent DNA strands. These results are discussed in relation to the mechanism of RK2 replication and in the context of the host range of the plasmid.
J Mol Biol 1988 Oct 20
PMID:Replication of mini RK2 plasmid in extracts of Escherichia coli requires plasmid-encoded protein TrfA and host-encoded proteins DnaA, B, G DNA gyrase and DNA polymerase III. 285 Mar 70

We constructed a recombinant plasmid containing the 2.1 kb HindIII fragment of plasmid pDG1, isolated from the cellular slime mold (Dictyostelium sp. strain GA11), and using pAG60 as cloning vector. We found that deletions of the recombinant plasmid took place frequently in Escherichia coli wild-type cells. However, the deletion was not observed when the plasmid was introduced into a strain that was an isogenic temperature-sensitive mutant of the gyrA gene. These results suggest that E. coli DNA gyrase is involved in the mechanisms of the deletion formation. It was shown that the 1.0 kb deletant derived from the 2.1 kb HindIII insert was produced by elimination of a 1.1 kb region. Sequence analysis of the deletants showed that cutting and rejoining took place between two out of the six nearly perfect direct repeats [21 bp palindromic sequences; AAAAAA(T/C)GGC(G/C)GCC(A/G)TTTTTT], located near the distal ends of the inverted repeats, preserving one copy of the repeats. These sequences consist of local short inverted repeats, where cutting and rejoining occur at one of the two regions.
Mol Gen Genet 1988 Sep
PMID:Formation of deletion in Escherichia coli between direct repeats located in the long inverted repeats of a cellular slime mold plasmid: participation of DNA gyrase. 285

Recently, the antitumor agent 4'-(9-acridinylamino)-methanesulfon-m-anisidide (m-AMSA) was shown to revert a frameshift mutant of T4 (rFC11), and its mutagenicity was shown to be mediated by T4 DNA topoisomerase II [Ripley et al.: J Mol Biol 200: 665-680, 1988]. Here we report dose-response data on the mutagenicity and toxicity of m-AMSA in T4 rFC11. We find that m-AMSA is among the most potent frameshift mutagens observed in T4, inducing a 10-fold increase in mutant frequency in the absence of toxicity and a 500-fold increase in mutant frequency at 31% survival. In addition to m-AMSA, the topoisomerase-active agents ellipticine, oxolinic acid, and nalidixic acid also reverted rFC11; however, they required concentrations 10-100 times greater than those required by m-AMSA in order to be mutagenic, and they did not produce mutant frequencies as high as those produced by m-AMSA. Unlike m-AMSA, all three agents were mutagenic only at toxic doses. The other agents evaluated--actinomycin D, adriamycin, 9-aminoellipticine, 9-methoxyellipticine, teniposide (VM-26), and novobiocin--were toxic but not mutagenic to T4 rFC11. Thus, m-AMSA appears to be distinctly different from the other topoisomerase-active agents in exhibiting such potent mutagenic activity in T4 rFC11. Because E. coli DNA gyrase may substitute for T4 topoisomerase II, we examined the ability of two inhibitors of E. coli DNA gyrase, novobiocin and nalidixic acid, to inhibit m-AMSA's mutagenicity. Both agents substantially reduced the mutagenicity of m-AMSA in T4 rFC11, further suggesting that topoisomerase mediates the mutagenicity of m-AMSA.
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PMID:Mutagenicity of topoisomerase-active agents in bacteriophage T4. 290 38

pBR322 DNA, linearized by lysis of an oxolinic acid-treated culture of Escherichia coli strain DK6recA- (pBR322) with sodium dodecyl sulfate, was purified, treated with DNA polymerase in the presence of the four deoxynucleoside triphosphates, and ligated to DNA linkers containing the XhoI recognition sequence. Most of the drug-resistant colonies resulting from transformation of E. coli with this material bore plasmids that appeared by restriction enzyme analysis to differ from pBR322 only by the introduction of an XhoI site. The XhoI sites in plasmids from 93 transformants were distributed unevenly around the pBR322 map. Maxam-Gilbert DNA sequence analysis of 36 of these plasmids, labeled at the 5' termini of the XhoI sites, revealed that 29 of them contained, in addition to the XhoI linker, a duplication of four base-pairs of the pBR322 sequence surrounding the linker. Therefore, oxolinic acid-induced linearization must have resulted in 5'-terminal extensions of four bases, the configuration known to result from oxolinic acid-induced DNA cleavage by DNA gyrase in vitro. The sequence data thus allowed the determination of the precise point at which linearization occurred, apparently by the abortion of a gyrase-DNA covalent intermediate that existed in vivo. When the 19 different sites of the 29 plasmids were compared, the following set of rules could be derived: (formula; see text) where N is any nucleotide, R is a purine, and Y is a pyrimidine. Cleavage occurred at the line between the eighth and ninth positions from the left. The parenthetical G and T were preferred secondarily to T and G, respectively, whereas T and G in the 13th position from the left were equally preferred. Several of these rules are similar to those proposed previously based on several in vitro gyrase cleavage sites. Some of our rules show dyad symmetry around the axis midway between the cleavage points in the two strands, while others are distinctly asymmetric.
J Mol Biol 1985 Jan 05
PMID:Sites of reaction of Escherichia coli DNA gyrase on pBR322 in vivo as revealed by oxolinic acid-induced plasmid linearization. 298 30

We have developed a procedure which permits the mapping of DNA gyrase cleavage sites in vivo. Addition of oxolinic acid, an inhibitor of DNA gyrase, to growing cells of Escherichia coli containing the plasmid pBR322 resulted in double-strand cleavage of DNA, and allowed the isolation of significant quantities of linearized plasmid DNA after lysis of treated cells with sodium dodecyl sulfate. Initially the linear product was purified from agarose gels, cleaved by restriction endonucleases, and then subjected to Southern hybridization analysis using defined DNA probes. A number of distinct cleavage sites, used with varying degrees of efficiency, were identified within pBR322 using this simple procedure. To achieve greater resolution and to improve sensitivity, we then employed an electroblotting procedure to transfer DNA fragments from acrylamide gels onto nylon membranes. This alternative method does not require the isolation of the linearized product before performing the mapping procedure. The improved resolution obtained from acrylamide gels and the superior binding properties of the nylon membranes have allowed us to accurately map 74 distinct oxolinic acid-induced cleavage sites within pBR322. The significance of these findings in light of previously reported studies in vitro, as well as the possible role of such sites during illegitimate recombination, are discussed.
J Mol Biol 1985 Feb 20
PMID:Mapping of DNA gyrase cleavage sites in vivo oxolinic acid induced cleavages in plasmid pBR322. 298 5

The effect of DNA superhelicity on the transcription of T4 DNA fragments containing early genes uvs W, Y and late genes 25-29 was studied. RNA polymerase transcribes both early and late phage genes within the supercoiled recombinant plasmid. Late genes relative transcription increases essentially when T4-modified RNA polymerase is used. DNA relaxation causes a sharp decrease of modified RNA polymerase activity, especially on the late genes. The same effect is obtained in intact cells with recombinant plasmid, which superhelicity is lowered by temperature-sensitive mutation in DNA gyrase. The data obtained prove that DNA superhelicity is required for the T4 late transcription by phage-modified RNA polymerase. It is suggested that the dependence of late transcription on the phage DNA replication in infected cells is connected with phage DNA superspiralization throughout its replication.
Mol Biol (Mosk)
PMID:[Effect of superhelical DNA on the transcription of cloned genes of the T4 phage]. 301 15

Indirect end-labelling and the digestion patterns of endogenous and exogenous nucleases were used to analyse chromatin organization along the ribosomal RNA genes of Dictyostelium discoideum cells. A zone just upstream from the 5' end of the coding region was particularly sensitive to endogenous nucleases. In exponentially growing cells, this hypersensitive zone extended from -350 to -1600 bp relative to the transcription start. In sharp contrast, the DNA between 0 and -350 bp was strongly protected. In differentiating cells, in which the ribosomal RNA transcription rate is low, the 5' hypersensitive zone was more diffuse than in exponentially growing cells, and the protected region at the 5' end of the transcribed region was less pronounced. It is known that where DNA topoisomerase is acting on DNA, the addition of sodium dodecyl sulphate will result in cleavage of the DNA and covalent attachment of the enzyme to the cut DNA end. Treatment of nuclei from both exponentially growing cells and differentiating cells with SDS caused double-stranded cleavages at -200 (i.e. within the protected region), at -2200, and at two sites at about -17 kb. A fraction of the cleavage products appeared to be strongly associated with protein. Novobiocin, a DNA topoisomerase II inhibitor, did not inhibit the SDS-induced cleavages in vegetative cells. However, it significantly reduced the extent of nuclease cleavage within the -350 to -1600 bp hypersensitive zone. The possibility is discussed that there are two DNA topoisomerase-like activities on the ribosomal genes. One is site-specific and novobiocin-insensitive. We speculate that the other is responsible for maintaining DNA at the 5' end of the gene in a torsionally strained, nuclease-hypersensitive state.
J Mol Biol 1986 Apr 05
PMID:Mapping of endogenous nuclease-sensitive regions and of putative topoisomerase sites of action along the chromatin of Dictyostelium ribosomal RNA genes. 301 83

The degradation of host DNA, and the block to transcription of cytosine-containing DNA, which are a part of the normal course of infection by bacteriophage T4, can be eliminated in an appropriate T4 genetic background (designated as our reference type, or r.t.), so that T4 late promoters carried on plasmid DNA can function. The changes of topoisomer distribution that ensue when phage T4 r.t. infect Escherichia coli carrying a plasmid containing a T4 late promoter were analyzed. The linking number of the covalently closed circular plasmid DNA increased (implying relaxation) at the same time as the distribution of topoisomers became much broader. The relaxation of plasmid DNA was primarily, but not exclusively, due to T4 DNA topoisomerase II. The bacterial DNA topoisomerase II (gyrase) continued to function after phage infection to maintain some degree of superhelicity in plasmid DNA. When the DNA gyrase was inhibited by coumermycin or oxolinic acid, the topoisomer distribution became distinctly bimodal, part of the DNA remaining highly negatively supercoiled. It is argued that the observed post-infection topological changes involve relaxation of torsional stress and changes of binding by proteins that topologically constrain the plasmid DNA.
J Mol Biol 1986 Aug 05
PMID:Topoisomerization of plasmid DNA in Escherichia coli infected with bacteriophage T4. 302 39


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