Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.1.27.1 (RNase)
16,360 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Transcription termination in vitro by vaccinia RNA polymerase is dependent on a trans-acting factor, VTF, that is associated with, if not identical to, the vaccinia mRNA capping enzyme. VTF-induced termination occurs approximately 50 nucleotides downstream of a signal sequence TTTTTNT in the non-transcribed templated strand; thus the cognate sequence UUUUUNU is expressed in the nascent RNA. To address the role of the nascent RNA in chain termination, the effects of nucleotide base analog substitutions were studied. Incorporation of bromo- (Br) UMP or iodo- (I) UMP into RNA abrogated factor-dependent termination without preventing the synthesis of read-through transcripts. Substitution of either ITP or 7'-methylguanosine for GTP did not inhibit factor-dependent termination, nor did the substitution of BrCTP or ICTP for CTP. The early transcripts synthesized in vitro were sensitive to RNase T2 but resistant to RNase H, indicating an absence of extensive hybridization of RNA product to the DNA template. Substitution of BrUTP for UTP did not alter the nuclease sensitivity of the transcripts, suggesting that increased stability of RNA:DNA hybrid structures did not account for the analog effects. These results are consistent with a model in which recognition of the primary sequence UUUUUNU in nascent RNA by the polymerase and/or VTF is required for transcription termination.
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PMID:Factor-dependent transcription termination by vaccinia virus RNA polymerase. Evidence that the cis-acting termination signal is in nascent RNA. 283 68

Using a cDNA probe complementary to an mRNA coding for the alpha-subunit of a human GTP-binding protein that stimulates adenylate cyclase we have studied its regional distribution in human brain by in situ hybridization histochemistry. The specificity of the hybridization signal was examined by using a labelled sense probe and RNase treatment. Gs alpha transcripts presented a widespread but heterogeneous distribution in human brain postmortem tissues. The cell bodies of the granular layer of the cerebellum were the most heavily labelled cells in all the cases examined. High levels of hybridization were also seen in the pyramidal cell layer of the hippocampus and over the cell bodies of the granule cells of the dentate gyrus. Several cortical regions also presented high levels of hybridization. Another area rich in the Gs alpha mRNA was the hypothalamus. The caudate and putamen nuclei presented intermediate levels while the globus pallidus, the thalamus, the midbrain and the brainstem presented only very low levels of hybridization. This distribution differs from the known distribution of adenylate cyclase activity and other GTP-binding proteins, and could indicate that this particular Gs alpha clone codes for a subset of the alpha-subunit of the Gs protein family.
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PMID:Regional distribution of the expression of a human stimulatory GTP-binding protein alpha-subunit in the human brain studied by in situ hybridization. 314 Oct 7

Stripped rough microsomes (SRM) fuse when incubated with physiological concentrations of GTP and MgCl2. In order to examine further to what extent such fusions are associated with other membrane functions of rough endoplasmic reticulum, we have evaluated the role of cytosolically exposed peptide constituents of SRM in fusion, and the possible relationship of GTP/MgCl2-induced fusion in protein transport across endoplasmic reticulum (ER) membranes, and in ER-Golgi interactions. Controlled proteolytic digestion of SRM led to the loss of fusion capability at 15 micrograms/ml trypsin--a concentration which maintained the latency of intraluminal mannose-6-phosphatase. Hence, a cytosolically exposed protein(s) regulated fusion. Based on ribonuclease-induced ribosome capping experiments, it was further concluded that the cytosolic oriented protein(s) was sequestered beneath the ribosome. As co-translational cell free translocation of placental lactogen across SRM was similar in control membranes compared to those rendered incapable of fusing, it was concluded that the fusion phenomenon may not be related to translocation. Under conditions promoting homologous fusion of SRM or Golgi membranes, mixtures of the two membranes showed no heterologous membrane fusion as assessed morphologically or by the transport of newly synthesized membrane glycoprotein. These experiments attest to the specificity of cytosolically exposed protein(s) in regulating nucleotide/divalent cation-induced membrane fusion.
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PMID:Properties of a GTP sensitive microdomain in rough microsomes. 382 32

The ribonuclease resistance assay has been used to probe the effect of trypsin modification of the Escherichia coli elongation factor Tu X GTP on the interaction with E. coli aminoacyl-tRNAs. First, the equilibrium dissociation constant of the trypsin-modified Tu X GTP X Thr-tRNA complex was determined to be 2.3 (0.1) X 10(-5)M at 4 degrees C, pH 7.4. Second, binding of 17 of 20 noninitiator aminoacyl-tRNAs and four sets of purified isoacceptor tRNAs to the modified protein was measured. At 4 degrees C, the complex stabilities vary 500-fold over the range of aminoacyl-tRNAs, with Gln-tRNA forming the strongest ternary complex and Val-tRNA, the weakest. The results are compared to a similar study of ternary complex formation using intact elongation factor Tu X GTP, and the major differences are discussed. An analysis of both data sets, particularly that for the leucine isoacceptor tRNAs, suggests that the trypsin modification of elongation factor Tu X GTP disrupts a region of protein that is involved with the aminoacyl side chain rather than that of the acceptor stem helix region of the aminoacyl-tRNA.
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PMID:Effect of trypsin modification of the Escherichia coli elongation factor Tu on the ternary complex with aminoacyl-tRNA. 389 46

The binding of ribosomes to mRNA is analyzed in a fractionated system from wheat germ with [3H]uridine-labeled poly(A)+ RNA prepared from germinating wheat embryos. The reaction requires factors eIF3, eIF4C, and eIF5; Met-tRNA and the Met-tRNA binding system; either GTP or GMP-PNP; ATP; and factors C1 and eIF4A. These requirements are identical to those previously found to be necessary for formation of ribosome X Met-tRNAMeti complexes, with the exception of ATP, and factors C1 and eIF4A. The function of factors C1 and eIF4A is therefore specifically related to the mRNA attachment reaction. The presence of GTP in the mRNA binding reaction results in the formation of 80 S ribosome complexes, while with GMP-PNP only 40 S ribosome complexes are formed. Ribosome binding to native reovirus RNA in the fractionated wheat germ system is similar to the reaction with poly(A)+ RNA, strongly requiring ATP and factors C1 and eIF4A. Binding to inosine-substituted reovirus RNA, however, is only partially dependent upon ATP, and both the ATP-dependent and the ATP-independent binding reactions strongly require factor C1 and are substantially stimulated by factor eIF4A. The ATP-independent reaction is inhibited by pm7GDP, has a strong requirement for Met-tRNAMeti, and the 40 S ribosome complex is stable to RNase. These results indicate that the ATP-independent binding of ribosomes to inosine-substituted reovirus RNA proceeds through the normal initiation process. They further suggest that neither factor C1 nor eIF4A function exclusively to unwind mRNA secondary structure. Since eIF4A is required for the ATP-independent binding to inosine mRNA, and at the same time interacts with ATP in the reaction with ATP-requiring mRNAs, this factor may have two roles in protein chain initiation, one related to the mRNA X ribosome interaction, and one related to the function of ATP.
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PMID:Initiation factors eIF4A and C1 from wheat germ and the formation of mRNA X ribosome complexes. 398 12

A cytosolic factor that stimulates transcription in isolated nuclei was purified approximately 4000-fold to near homogeneity from rat liver. The molecular weight of the factor was determined as 47 000 by SDS-polyacrylamide gel electrophoresis. The factor had no detectable deoxyribonuclease and protease activity but showed ribonuclease inhibitor activity. The factor could stimulate transcription in isolated nuclei by 50% at about 3.0 ng and the maximal stimulation was about 100%. When [gamma-S]ATP and [gamma-S]GTP were included in the reaction, the factor stimulated the synthesis of RNA which was able to bind to a mercury-Sepharose column and about 80% of the bound RNA was sensitive to a low concentration of alpha-amanitin. When heparin was added before initiation to preincubation mixture containing RNA polymerases II and DNA, a small but definite incorporation of [14C]UTP was observed. The factor alone had no stimulatory effect on the heparin-resistant incorporation of [14C]UTP but, in the presence of two rat liver nuclear fractions, phosphocellulose 0.5 and 1 M KCl step fractions, could stimulate the incorporation above the level with the combination of the two nuclear fractions. Antibody raised against the factor inhibited accurate transcription from the adenovirus 2 major late promoter in a nuclear lysate from Ehrlich ascites tumor cells, and the inhibition was neutralized by the factor.
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PMID:Purification of a cytosolic factor from rat liver that stimulates transcription in isolated nuclei and its action on purified RNA polymerase II-DNA system. 407 43

Treatment of insect polyribosomes with 1 M KCl released a messenger ribonucleoprotein with a pronounced 16S peak. Phenol extraction resulted in a defined peak of 10S RNA, which was judged as mRNA by the following criteria: it showed specificity for binding to ribosomes, and the formation of initiation complex was dependent on protein initiation factors, GTP, mRNA, and aminoacyl-tRNA. The complex directed protein synthesis upon the addition of elongation factors. mRNA was treated with phosphatase and phosphorylated at the 5'-end with [(32)P]cyanoethylphosphate. [(32)P]mRNA was digested by T1 ribonuclease to completion and chromatographed on DEAE-cellulose. The only fragment with (32)P was 15 nucleotides long; it was treated with pancreatic ribonuclease and fingerprinted. Fractions of AC, AAC, and AAAC were found. Initiation signal AUG or GUG in these mRNAs does not begin immediately at the 5'-end and may be at a distance greater than 15 nucleotides. Alkaline hydrolysis of mRNAs labeled in vivo with [(14)C]adenosine revealed Ap and pppAp. Alkaline hydrolysis of mRNA labeled with (32)P at the 5'-terminus resulted in pAp. Hence, these results suggest that in a heterogeneous population of mRNAs from insects, all start with A and have sequence homology at the 5'-termini. This sequence may reflect the signal for RNA polymerase on the gene or may promote the binding of mRNA to ribosomes.
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PMID:Sequence homology at the 5'-termini of insect messenger RNAs. 435 Nov 73

Rat liver mitochondria isolated in sucrose-N-tris(hydroxymethyl)methyl-2-aminoethane-sulphonic acid (TES) incorporated [(3)H]UTP into RNA for 1h. Incorporation was inhibited 50% by 1mug of actinomycin D/ml, 1mug of acriflavine/ml and 0.5mug of ethidium bromide/ml but was insensitive to rifampicin, rifamycin SV, streptovarcin and deoxyribonuclease. After the first 10min of incubation, the synthesis was insensitive to ribonuclease. RNA synthesis by mitochondria isolated in sucrose-EDTA was insensitive to actinomycin D and sensitive to ribonuclease during the first 10min of the incubation but thereafter the sensitivities were the same as for mitochondria isolated in sucrose-TES. In a hypo-osmotic medium the relative extent of incorporation of the four ribonucleoside triphosphates into RNA was CTP>UTP=ATP>>GTP. In an iso-osmotic medium the incorporation of CTP and GTP decreased. All four nucleotides were incorporated into RNA in a DNA-dependent process, as indicated by the inhibition by actinomycin D. In addition, CTP and ATP were incorporated into the CCA end of mitochondrial tRNA. ATP was also incorporated into an unidentified acid-insoluble compound, which hydrolysed in alkali to a product that was not ATP, ADP or 5'- or 2(3')-AMP. Atractyloside inhibited the incorporation of ATP into RNA with 50% inhibition at 2-3nmol/mg of protein. The [(3)H]UTP-labelled RNA had peaks of 16S and 13S characteristic of mitochondrial rRNA. In addition a peak at 20-21S was observed as well as heterogeneous RNA sedimenting throughout the gradient. The synthesis of all these species was inhibited by actinomycin D, indicating that rat liver mitochondrial DNA codes for mitochondrial rRNA as well as other as yet unidentified species.
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PMID:Synthesis of ribonucleic acid by isolated rat liver mitochondria. 440 94

Poly(A) polymerase activity is induced during vaccinia virus infection of HeLa cells. The enzyme is maximally induced at 3.5 h postinfection. Partial purification frees the preparation of RNase activity and RNA polymerase activity. ATP is the substrate for poly(A) synthesis. A small amount of poly(A) is produced from added adenosine diphosphate due to the production of ATP by an adenylate kinase present in the preparation. The incorporation of ATP into poly(A) is dependent on divalent cations (Mg(2+) or Mn(2+)) and is not inhibited by UTP, CTP, or GTP. Poly(U) stimulates ATP incorporation; poly(A) and poly(C) have little effect on ATP incorporation, and poly(dT) is extremely inhibitory. RNA prepared from HeLa cells and from the partially purified poly(A) polymerase (the enzyme preparation contains endogenous RNA [Brakel and Kates]) stimulates ATP incorporation by poly(A) polymerase which was subjected to DEAE-cellulose chromatography. RNase's, pancreatic and T(1), inhibit the production of poly(A). DNase has little effect. Poly(U) is able to stimulate poly(A) production in the presence of T(1) RNase.
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PMID:Poly(A) polymerase from vaccinia virus-infected cells. I. Partial purification and characterization. 441 6

A new RNase activity, tentatively named RNase V, was found in cell-free extracts of E. coli. This activity requires ribosomes, G and T factors, tRNA, K(+) or NH(4) (+), Mg(2+), GTP, and a sulfhydryl compound to degrade poly U, poly A, T4 phage mRNA, or E. coli mRNA. RNase V is specific for mRNA; it does not attack ribosomal RNA. It is inhibited by antibiotics that decrease breakdown of mRNA in vivo, such as chloramphenicol and streptomycin, and by such agents as 5'-beta, gamma-methylene-guanosine triphosphate, and fusidic acid, which inhibit ribosome-dependent GTPase and translocation of ribosomes along mRNA. The evidence suggests that RNase V is either an integral part of the ribosome or is tightly associated with it, and that it selectively degrades mRNA in intact cells.
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PMID:Ribonuclease V of escherichia coli. I. Dependence on ribosomes and translocation. 490 7


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