Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.7.6 (RNA polymerase)
 34,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

RNA transcribed in isolated sea urchin nuclei and assayed by hybridization to histone genes cloned in E. coli contains sequences homologous to each of the five histone genes. Histone RNA is synthesized exclusively from the same DNA strand which is the template in vivo. Synthesis of the histone gene transcripts is sensitive to alpha-amanitin concentrations which inhibit RNA polymerase II activity. The fraction of histone RNA synthesized in vitro is comparable at two developmental stages to the fraction synthesized in vivo. The nuclear histone transcripts contain sequences homologous to spacer DNA regions present between the coding regions of the 6500 base pair (bp) histone gene repeat unit. The transcription of spacer sequences was demonstrated by hybridization of the nuclear transcripts to subcloned spacer DNA. Although the bulk of the RNA transcripts are greater than 2000 bases long, the histone-specific transcripts are of discrete sizes ranging from 100 bases to about 1100 bases long. Each histone gene hybridizes with at least one of the larger transcripts and with a different subset of smaller RNAs. We do not detect any giant polycistronic transcript spanning the entire histone repeat unit.
Cell 1978 Sep
PMID:Sea urchin nuclei use RNA polymerase II to transcribe discrete histone RNAs larger than messengers. 69 39

DRB triphosphate inhibits activity of isolated RNA polymerase B, and, to a lesser extent, that of polymerase A. The same holds true for transcription in isolated nuclei. It does not act as an initiation inhibitor. In all cases, high concentrations of DRB triphosphate are required. Cells do not phosphorylate DRB to a measurable extent. hn RNA resistant to DRB is initiated with both ATP and GTP in the presence of the drug. These experiments render the hypothesis unlikely that DRB triphosphate in the cell specifically interferes with the initiation reaction of polymerase B.
Nucleic Acids Res 1978 Sep
PMID:Inhibition of mammalian RNA polymerase by 5,6-dichlororibofuranosylbenzimidazole (DRB) and DRB triphosphate. 70 59

The actively growing cells (trophozoites) of the amoeba Acanthamoeba castellanii were found to contain three or perhaps four different forms of class II DNA-dependent RNA polymerase (EC 2.7.7.6). The chromatographic and catalytic properties of all forms of the Acanthamoeba class II polymerases suggest them to be cognates of the class II polymerases previously reported. The predominant form was purified to near homogeneity and its subunit composition determined. Nine different polypeptides were found associated with the purified enzyme: 21 000; 185 000; 140 000; 70 000; 35 000; 21 000; 19 000; 18 500 and 16 200. These polypeptides were interpreted in terms of two class II RNA polymerases which differ in the molecular weight of their largest subunit. When A. castellanii is transferred to a medium lacking nutrients, the cells undergo cellular differentiation resulting in the formation of metabolically inactive cells (cyst formation). During this process there are significant changes in the RNA sequences transcribed. In contrast to this, we find that the chromatographic and catalytic properties of all of the class II RNA polymerases remain unchanged. Further, the subunit architecture of the predominant form(s) of polymerase II is unaltered. These findings suggest that although new RNA sequences are transcribed during encystment their appearance is not a consequence of extensive alterations in the subunit composition of the major class II RNA polymerase.
Biochim Biophys Acta 1978 Sep 27
PMID:DNA-dependent RNA polymerase II from Acanthamoeba castellanii. Comparison of the catalytic properties and subunit architectures of the trophozoite and cyst enzymes. 70 41

DNA-dependent RNA polymerases were solubilized from developing wings of the oak silkmoth, Antheraea pernyi, and partially purified by ion-exchange chromatography and sucrose gradient sedimentation. Four enzyme species were resolved on the basis of chromatographic behavior, divalent cation requirements, ionic strength optima, template preference and alpha-amanitin sensitivity. Each class (i.e. RNA polymerase I and II) was present in two forms termed IA, IB and IIA, IIB on the basis of their elution pattern from the column. Both class I enzymes were sensitive to high concentrations of alpha-amanitin but this may be due to general toxicity rather than specific inhibition. The intraclass variants did not differ significantly in enzymatic properties although form IIB was more sensitive to alpha-amanitin (50% inhibition at 2 . 10(-9) M) than form IIA (3 . 10(-8)M).
Biochim Biophys Acta 1978 Sep 27
PMID:Evidence for the existence of two forms of RNA polymerases I and II in insect wing epidermis. 70 42

Localized mutagenes of Salmonella typhimurium followed by a [3H]uridine enrichment procedure yielded a temperature-sensitive strain with a mutation in the rpo region of the chromosome. Ribonucleic acid (RNA) polymerase (EC 2.7.7.6; nucleoside triphosphate: RNA nucleotidyltransferase) purified from this mutant was considerably less active at the nonpermissive temperature than wild-type enzyme. Furthermore, the enzyme from this mutant, unlike RNA polymerase of previously isolated temperature-sensitive mutants, was as thermostable as wild-type enzyme when preincubated at 50 degrees C. Subunit reconstitution experiments have shown that the temperature sensitivity is caused by an alteration in the beta' subunit of the enzyme.
J Bacteriol 1976 Sep
PMID:Temperature-sensitive ribonucleic acid polymerase mutant of Salmonella typhimurium with a defect in the beta' subunit. 78 38

The effect of estrogen on gene expression in the chick oviduct was investigated. Studies on the effect of the temperature requirement for ribonuclei acid (RNA) chain initiation by Escherichia coli RNA polymerase on deoxyribonucleic acid (DNA), chromatin, and reconstituted chromatin were carried out to better understand the nature of the initiation process. Varying the temperature or ionic strength during preincubations had little effect on the formation of stable preinitiation complexes between RNA polymerase and chromatin. This was in contrast to similar studies performed on native DNA and indicates that initiation sites for RNA synthesis on chromatin are different from those on double-stranded DNA and resemble more closely initiation of RNA synthesis on single-stranded DNA. These observations suggest that the local unwinding of the initiation region which is required for RNA chain initiation on native DNA may not be a prerequisite for RNA initiation on chromatin. Studies on reconstituted chromatin devoid of different classes of chromatin proteins demonstrate that both histone and nonhistone fractions are essential inmaintaining the charcteristics inherent to initiation of RNA synthesis on chrmatin. Removal of moderately lysine-rich histone or arginine-rich histone fractions led to the complete loss of the characteristic ''chromatin type'' initiation pattern for RNA synthesis whereas removing lysine-rich (F1) histone had no effect. Additional studies suggest that initiation sites on chromatin are not located in freely accessible single- or double-stranded regions of DNA.
J Biol Chem 1976 Sep 25
PMID:Effect of estrogen on gene expression in the chick oviduct. Studies on the initiation of RNA synthesis on chromatin in vitro. 78 84

Methods developed for isolating bacterial nucleoids were applied to bacteria infected with phage T4. The replicating pool of T4 DNA was isolated as a particle composed of condensed T4 DNA and certain RNA and protein components of the cell. The particles have a narrow sedimentation profile (weight-average s=2,500S) and have, on average, a T4 DNA content similar to that of the infected cell. Their dimensions observed via electron and fluorescence microscopy are similar to the dimensions of the intracellular DNA pool. The DNA packaging density is less than that of the isolated bacterial nucleoid but appears to be roughly similar to its state in vivo. Host-cell proteins and T4-specific proteins bound to the DNA were characterized by electrophoresis on polyacrylamide gels. The major host proteins are the RNA polymerase subunits and two envelope proteins (molecular weights, 36,000 and 31,000). Other major proteins of the host cell were absent or barely detectable. Single-strand breaks can be introduced into the DNA with gamma radiation or DNase without affecting its sedimentation rate. This and other studies of the effects of intercalated ethidium molecules have suggested that the average superhelical density of the condensed DNA is small. However, these studies also indicated that there may be a few domains in the DNA that become positively supercoiled in the presence of high concentrations of ethidium bromide. In contrast to the Escherichia coli nucleoid, the T4 DNA structure remains condensed after the RNA and protein components have been removed (although there may be slight relaxation in the state of condensation under these conditions).
J Virol 1976 Sep
PMID:Properties of condensed bacteriophage T4 DNA isolated from Escherichia coli infected with bacteriophage T4. 78 57

RNA polymerase from T4 infected cells supplemented with E. coli sigma polypeptide has a lower affinity for rRNA promoters than RNA polymerase from uninfected cells. The pattern of transcription by the phage modified polymerase is qualitatively similar to that of the vegetative polymerase in the presence of ppGpp. We suggest that E. coli polymerase holoenzyme normally exists in at least two conformational states, one with a high affinity for rRNA promoters and another with a low affinity, and that T4 infection stabilises the low affinity form.
Mol Gen Genet 1976 Sep 23
PMID:Phage T4 infection restricts rRNA synthesis by E. coli RNA polymerase. 78 64

RNA polymerase isolated from ts XH56, a conditional lethal mutant unable to grow and synthesize RNA at 42 degrees, was found to be temperature sensitive in vitro. The mutation affects the beta' subunit as determined by mixed reconstitution of isolated subunits from wild-type and mutant enzyme. The mutant RNA polymerase is unstable; addition of glycerol stabilizes the enzyme and increases its activity on native DNA. In addition, the mutant enzymes is sensitive to high ionic strength. Both high temperature and high ionic strength do not affect chain elongation; thus, the mutation renders the enzyme unable either to bind to or melt out promotor sites. From these data we conclude that the beta' subunit plays an important role in promotor selection.
Mol Gen Genet 1976 Sep 23
PMID:Characterization of a ts beta' mutant RNA polymerase of Escherichia coli. 78 68

Using an assay specific for chain elongation of E. coli RNA polymerase the kinetics of this propagation reaction have been studied. The kinetic behaviour is consistent woth the mathematical model formulated for this multisubstrate enzyme. The effect of increasing salt concentration on the kinetics of the reaction indicated that DNA unwinding is probably a necessary step in the propagation step, although this may not be the rate limiting step under all conditions.
Nucleic Acids Res 1976 Sep
PMID:The kinetics of E. coli RNA polymerase. 78 32


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>