共查询到20条相似文献,搜索用时 15 毫秒
1.
J Germershausen D Goodman E W Somberg 《Biochemical and biophysical research communications》1978,82(3):871-878
RNA (guanine-7) methyltransferase, partially purified from mycelia, catalyzed the transfer of the methyl group from S-adenosylmethionine to the 5′ terminus of both poly A(+) RNA and reovirus unmethylated mRNA. RNase T2 digestion of the methylated poly A(+) RNA from yielded the “cap” structures m 7G(5′)pppAp and m 7G(5′)pppGp in a ratio of 2:1 respectively. RNase T2 digestion of the methylated reovirus mRNA yielded m 7G(5′)pppGp exclusively. The absence of mRNA 2′-0-methyltransferase activity in the enzyme preparation is consistent with the absence of 2′-0-methylation in mRNA [Seidel, B. L. and Somberg, E. W. (1978) Arch. Biochem. Biophys. , 108–112]. This is the first isolation of an eucaryotic, cellular RNA (guanine-7) methyltransferase that has been shown to methylate homologous substrate. 相似文献
2.
The RNA products synthesized by the virion-associated RNA polymerase of purified vesicular stomatitis virus have previously been shown to contain two distinct 5′-terminal sequences. The mRNA species contain the blocked 5′-terminal G(5′)ppp(5′)A-A-C-A-G sequence and the initiated lead-in RNA segment (approximately 50 bases) contains the unblocked 5′ ppA-C-G sequence. In the present studies, using inosine 5′-triphosphate in place of GTP it is shown that RNA species as large as 14.5S contain an unblocked 5′-ppA-C-(I) sequence indicating that the GTP analogue permits synthesis of a possible precursor of viral mRNA . 相似文献
3.
Christine K. Carrico Linda S. Cunningham Alan C. Sartorelli 《Biochemical and biophysical research communications》1977,78(4):1204-1210
6-Thioguanine was administered to rats 12 hr after partial hepatectomy at a dose of 40 mg/kg of body weight; 6 hr later, polyadenylic acid-containing RNA was isolated and was used to measure initiation of protein synthesis in a wheat germ system. initiation was found to be 2.3-fold greater when 6-thioguanine-containing RNA was employed, than when polyadenylic acid-containing RNA isolated from untreated animals was used. The homopolymer, poly(TG), did not promote peptide synthesis in the wheat germ system employed. 相似文献
4.
N-6-methyl-adenosine in adenovirus type 2 nuclear RNA is conserved in the formation of messenger RNA 总被引:18,自引:0,他引:18
In the biogenesis of adenovirus type 2 messenger RNAs, methylation occurs at the 5′ end (cap) and to internal adenosine residues to yield N6-methyl-adenosine (m6A) (Sommer et al., 1976; Moss &; Koczot, 1976; Wold et al., 1976). The kinetics of accumulation of 3H from methyl-labeled methionine and 14C from uridine into Ad-22-specific RNA was measured late in Ad-2 infection. As reported previously (Nevins &; Darnell, 1978a), the rate of accumulation of [14C]uridine label in nuclear RNA was approximately four- to fivefold faster than in the cytoplasmic RNA, indicating a conservation of about 20% for the total RNA. The initial rates of [3H]methyl label in m6A in nuclear RNA and in the cytoplasmic RNA were approximately equal, suggesting a complete (or nearly complete) conservation of m6A.In accord with the accumulation kinetics, the ratio of 3H to 14C was higher in cytoplasmic RNA than in nuclear RNA that hybridized to equivalent regions of the Ad-2 DNA.A mathematical model was designed to evaluate the accumulation of methyl label in m6A, taking into consideration the three major parameters that affect the accumulation curves: equilibration of the S-adenosyl-methionine pool, the nuclear dwell time of sequences destined to be mRNA, and the cytoplasmic stability of mRNA. The half-time () for pool equilibration was determined experimentally to be 22 minutes and the nuclear dwell time and the mean life-time of cytoplasmic mRNA were estimated from 14C label to be about 30 and 70 minutes, respectively.The model gave an excellent fit to the data when the for pool equilibration time of 24 ± 2 minutes, a nuclear dwell time of 25 ± 10 minutes, and a mean cytoplasmic mRNA life-time of 75 ± 30 minutes were used to evaluate accumulation curves. Even when data from a restricted region of the genome, , which encodes the main portion of at least five 3′ co-terminal mRNAs whose spliced junction with the tripartite leader sequence varies from , and was analyzed, it appeared that m6A was conserved.Finally, m6A was found to be added in a brief label (3.5 min) mainly to nuclear molecules that were longer than any cytoplasmic RNA. The conservation of m6A and its addition prior to splicing raise the possibility that internal methylations are involved, in the formation of mRNA. 相似文献
5.
A rat liver nuclear envelope fraction isolated essentially by the technique of Monneron et al. (J. Cell Biol. 55, 104–125 (1972)) is characterized by high levels of glucose-6-phosphatase and 5′-nucleotidase. A broadly specific nucleoside triphosphatase activity is present. Cytochromes and as well as NADPH- and NADH-cytochrome reductase activities are present but at lower levels than found in microsomes. Cytochrome oxidase activity is low. RNA polymerase activity is absent from the nuclear envelope fraction. Cytochemistry shows that glucose-6-phosphatase activity is strong and restricted to the nuclear envelope of nuclei. 5′-Nucleotidase shows weak reaction deposit in whole nuclei but in contrast gives clear reaction deposit in isolated nuclear envelopes. Cytochemical reaction deposit due to nucleoside trisphosphatase activity is not restricted to the nuclear envelope but is found to a larger extent within the nucleus. 相似文献
6.
α factor is a diffusible substance produced by cells of the mating type which inhibits cell division (1) and the initiation of nuclear DNA synthesis (2) in cells of the mating type. In this report, it is shown that mitochondrial DNA synthesis continues at a normal rate in cells for at least 6 hours in the presence of α factor, resulting in a 5-fold increase in the amount of mitochondrial DNA per cell. The continued synthesis of mitochondrial DNA in the absence of nuclear DNA synthesis allows specific labeling of yeast mitochondrial DNA. 相似文献
7.
F L Yu 《Biochemical and biophysical research communications》1975,64(3):1107-1115
Rat liver nuclei, seventeen hours after partial hepatectomy, showed a two to three-fold increase in total RNA synthesis over the sham operated controls. When tested with exogenous synthetic template, this was found to be mainly a reflection of increased levels of both the nuclear free and engaged RNA polymerase activities . It was also observed that there was a greater stimulation of the species of RNA polymerase that are α-amanitin resistant than sensitive (3.2 μg/ml). This observation was further confirmed by DEAE-Sephadex column chromatography of the solubilized nuclear free and engaged RNA polymerases and found RNA polymerase I and IIIa were the major species greatly stimulated during this period of liver regeneration. These data suggest not only that there exists a sensitive equilibrium between the nuclear free and engaged RNA polymerases; they also suggest the possibility that RNA polymerase itself may play a positive role in the regulation of gene expression. 相似文献
8.
S Friedman 《Biochemical and biophysical research communications》1979,89(4):1328-1333
5-Azacytidine, when added to growing K12, causes a decrease in DNA methylation assayed . This decrease is greater when DNA is used as substrate than when calf thymus DNA is used. The decrease in activity is not due to the inhibition of protein synthesis caused by this drug, since neither chloramphenicol nor rifampin causes a decrease in enzyme activity. The effect is specific for the DNA(cytosine-5)methylase; the methylation of adenine is not affected. The concentration of drug that inhibits the DNA methylase by 50% is the same concentration that inhibits cell growth by 50%. 相似文献
9.
10.
1H nuclear magnetic resonance spectra of 1 - (II) and 3-deazaadenosines (III) together with adenosine (I) in dimethylsulfoxide have been examined. Features of coupling constants indicate that the furanose rings of I, II, and III have similar conformational preferences and that conformations about the 4′-C–5′-C bond are preferentially . Nuclear Overhauser effect and spin-lattice relaxation-time measurements demonstrate that II predominantly adopts the -conformation similar to that of I, whereas that of III has a greater (freely rotating) component. The results suggest that the -conformation in II as well as I is stabilized presumably through a hydrogen bond between the 3-N and 5′-hydroxyl group. 相似文献
11.
Primary structure of E. coli alanine transfer RNA: relation to the yeast phenylalanyl tRNA synthetase recognition site 总被引:11,自引:0,他引:11
R J Williams W Nagel B Roe B Dudock 《Biochemical and biophysical research communications》1974,60(4):1215-1221
Nucleotide sequence comparison of tRNAs aminoacylated by yeast phenylalanyl tRNA synthetase (PRS) have lead to the proposal that the specific nucleotides of the dihydrouridine (diHU) stem region and adenosine at the fourth position from the 3′ end are involved in the PRS recognition site. Kinetic analysis and enzymatic methylation have shown that the size of the diHU loop and the methylation of guanine at position 10 from the 5′ end both directly affect the PRS aminoacylation kinetics. tRNA1A1a, which is aminoacylated by PRS, should therefore have 1- the specific nucleotides of the diHU stem region and, 2- adenosine at position 4 from the 3′ end. The PRS aminoacylation kinetics of this tRNA indicates that this molecule 3- has a diHU loop of 8 nucleotides and 4- has an unmethylated guanine at position 10 from the 5′ end. We report here the complete sequence of tRNA1A1a and confirmation of each of these four predictions. 相似文献
12.
13.
Neomycin inhibits DNA dependent DNA and RNA synthesis catalyzed by DNA polymerase I and RNA polymerase from . The effect of the antibiotic is more pronounced towards DNA synthesis. The inhibition of DNA synthesis is competitive with template DNA, does not reverse with excess deoxynucleoside triphosphate, Mg2+ or enzyme DNA polymerase I. Neomycin does not reduce the number of potential 3′ -OH end or primer. It seems to shorten the size of the newly formed polynucleotide. 相似文献
14.
Susan Peacock Nathan Brot Herbert Weissbach 《Biochemical and biophysical research communications》1983,113(3):1018-1025
Using the plasmid pNF1337 as template, a mRNA preparation has been obtained that directs the synthesis of fMet-Val, the N-terminal dipeptide of the β subunit of RNA polymerase. RNA polymerase holoenzyme specifically inhibits the mRNA-directed synthesis of fMet-Val showing that the autoregulation by RNA polymerase of β,β′ synthesis is at the level of translation. L factor ( gene product) stimulates the synthesis of fMet-Val from a DNA template but not from mRNA. Rifampicin has no effect on the mRNA-directed synthesis of fMet-Val or the ability of RNA polymerase to inhibit fMet-Val synthesis. 相似文献
15.
Mrunal S. Chapekar Robert I. Glazer 《Biochemical and biophysical research communications》1983,115(1):137-143
The effect of the cordycepin trimer analog of (A2′p)2A on cell growth, cell viability and nucleic acid synthesis was assessed in human colon carcinoma cell line HT-29 . The cordycepin analog, (3′dA2′p)23′dA reduced 24 hr cell growth by 50% at 10?4M and decreased cell viability by 98% under these conditions. The cytotoxicity and inhibitory effects of (3′dA2′p)23′dA on DNA and RNA synthesis were potentiated 5–10-fold by the presence of the adenosine deaminase inhibitor, 2′-deoxycoformycin, and closely resembled those of the parent drug, cordycepin. Chromatographic analyses of the stability of (3′dA2′p)23′dA in the tissue culture medium indicated that it was hydrolyzed to the dimer and monomer forms with a half life of approximately 2 hr. No intact (3′dA2′p)23′dA was detectable intracellularly, but large concentrations of cordycepin nucleotide metabolites were formed, particularly in the presence of 2′-deoxycoformycin. 相似文献
16.
Ronald E. Law Ralph M. Sinibaldi Michael R. Cummings Adolph J. Ferro 《Biochemical and biophysical research communications》1976,73(3):600-606
5′-Methylthioadenosine (MTA) inhibits the incorporation of [3H] uridine into RNA in salivary glands of . This effect is not due to an inhibition of [3H] uridine uptake into the glands. The inhibition of RNA synthesis by MTA is concentration dependent and maximum inhibition is observed after 45 minutes of incubation in the presence of 1 mM MTA. Experiments utilizing α-amanitin suggest that the synthesis of heterogeneous RNA is completely inhibited. 相似文献
17.
Leukemic guinea pig lymphocytes (L2 C) synthesise cholesterol in vitro at a forty-fold greater rate than normal cells. Equilibration (18 h) with lecithin or lecithin-cholesterol liposomes, respectively, enhances or suppresses sterol manufacture by normal lymphocytes but does not influence sterol production by L2 C cells. In contrast, molecules/cell of a nitroxide-derivative of androstane, (17 β-hydroxy-4′,4′-dimethylspiro [5 α-androstan-3,2′-oxazolidin]-3′-yloxyl), commonly used as a membrane spin-probe, drastically inhibit sterol production by both normal and leukemic cells (maximum within 2 h). At molecules/cell, this sterol stimulates cholesterol synthesis. 25-Hydroxycholesterol at low concentrations also stimulates sterol manufacture, whereas high concentrations are also inhibitory in both cell types. 相似文献
18.
Malcolm MacCoss Eung K. Ryu Tatsuo Matsushita 《Biochemical and biophysical research communications》1978,85(2):714-723
Recently, 1-β--arabinofuranosylcytosine-5′-diphosphate--1,2-dipalmitin (VIa) was reported to inhibit the growth of L51784 cells in mice and of human colon carcinoma HCT-15 cells, also in mice. This paper describes the synthesis of a single diastereomer by conversion of 1-β--arabinofuranosylcytosine 5′-monophosphate (II) to the nucleoside 5′-phosphomorpholidate (III), followed by reaction with -α-dipalmitoylphosphatidic acid (IV) to give 1-β--arabinofuranosylcytosine-5′-diphosphate--1,2-dipalmitin (V) in good yield. The separation of the product is described and its characterization by chromatography, elemental analysis, and spectroscopic methods. The lipophilic nature of V renders it insoluble in aqueous media and a method of sample preparation utilizing sonication techniques is described which provides a clear solution suitable for biological evaluation. In addition, the ability of V to inhibit the growth of L1210 cells and of mouse myeloma MPC 11 cells is desscribed and compared with 1-β--arabinofuranosylcytosine (I) and other lipophilic prodrugs of I. 相似文献
19.
Ramachandra Reddy Dale Henning Harris Busch 《Biochemical and biophysical research communications》1981,98(4):1076-1083
The primary nucleotide sequence was reported earlier for U1 RNA (Reddy et al, (1974) J. Biol. Chem. , 6486–6494), an snRNA implicated in splicing of HnRNAs. In view of the presence of homologous pseudouridine (ψ) residues in 5′-ends of several highly conserved U-snRNAs and the recent report of modified bases in the U1 RNA structure (Branlant et al, (1980) Nucleic Acids Res. , 4143–4154) a study was made for the presence of ψ and other modified nucleotides in the 5′-end of the U1 RNA. Identification of ψ residues at positions 6 and 7, shows the 5′-sequence of U1 RNA is: m32, 2,7 GpppAm-Um-A-C-ψ-ψ-A-C-C-U-G-G-C-A-G-G-G-G-A-G-A-U-A-C. The ψ residues in place of U at positions 6 and 7 may affect the binding of U1 RNA at intron-exon splice junctions. 相似文献
20.
James L. White 《Biochemical and biophysical research communications》1978,83(3):1099-1104
3′-deoxyadenosine triphosphate inhibited [3H]UMP incorporation by RNA-dependent RNA polymerases from tobacco and cowpea plants. The inhibition of [3H]UMP incorporation could be reversed by simultaneous addition of higher ATP concentrations but not with increasing concentrations of UTP or when excess ATP was added 10 min after the inhibitor. These results suggest 3′-deoxyadenosine triphosphate competes specifically with ATP in reaction mixtures and results in premature termination of RNA synthesis by RNA-dependent RNA polymerase. 相似文献