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At least 487 records · Page 27Linked to original sources
PubMed1967

Ribonucleic acid polymerase catalyzing synthesis of double-stranded arbovirus ribonucleic acid.

The large-particle fraction from the cytoplasm of chick embryo fibroblasts infected with Semliki Forest virus was found to catalyze the incorporation of the 5'-triphosphates of guanosine, adenine, cytidine, and uridine into an acid-insoluble alkali-labile product. The conditions affecting the preparation and assay of this enzyme were investigated. The ribonucleic acid (RNA) polymerase was not present in uninfected cells, and it appeared in infected cells at the time of rapid viral RNA synthesis. The polymerase was found to catalyze the synthesis of a species of RNA which was resistant to ribonuclease and which exhibited the sedimentation properties, buoyant density, and thermal transition temperature of the double-stranded RNA found in vivo in chick cells infected with Semliki forest virus. Attempts to demonstrate that the reaction product of this enzyme also included single-stranded viral RNA were not successful. Although other interpretations are possible, these results give some support to the suggestion that more than one enzyme may be involved in the replication of viral RNA.

Adenosine Triphosphate↗
PubMed1969

Ribonucleic acid synthesis of vesicular stomatitis virus. I. Species of ribonucleic acid found in Chinese hamster ovary cells infected with plaque-forming and defective particles.

Plaque-forming B particles of vesicular stomatitis virus (VSV) induce the synthesis of virus-specific ribonucleic acid (RNA) in Chinese hamster ovary cells, whereas defective T particles do not. Infection with low input multiplicities of B results in the formation of four species of RNA. During infection with high multiplicities, RNA synthesis begins with mainly these four species of RNA but gradually shifts to a new pattern of RNA synthesis involving five other species of RNA. The change can also be induced by superinfection with T at 2.5 hr after infection with a low multiplicity of B. T added at the same time as B prevents virtually all RNA synthesis. Synthesis of the first group of RNA species correlates with the formation of B particles, whereas synthesis of the second group correlates with the formation of T particles. The various species of RNA formed after infection with VSV particles include single-stranded RNA, a completely double-stranded RNA, and RNA with partially double-stranded regions. These observations begin to establish a molecular basis for understanding the ability of T particles to interfere with the growth of B particles.

Animals↗
PubMed1981

Heavy-chain mutants derived from gamma 2b mouse myeloma: characterization of heavy-chain messenger ribonucleic acid, proteins, and secretion in delection mutants and messenger ribonucleic acid in gamma2a mutant progeny.

Mouse myeloma mutants isolated from cell line 45.6 (gamma 2b) producing structurally altered immunoglobulin heavy (H) chains have been characterized. The mutant 10-1 synthesizes an H chain of 47 000 daltons containing a CH1 deletion; two mutants, G251 and I17, derived from 10-1 synthesize H chains of 40 000 and 35 000 daltons, respectively. The messenger ribonucleic acids (mRNAs) in these mutants have been shown to be smaller in molecular weight than mRNAs produced in 45.6 cells and lack a portion, but not all, of the CH1 domain. The H chains of G251 and I17 no longer express IgG subclass-specific determinants, are not secreted, and are structurally altered in the carboxyl-terminal portion of the molecule. In vitro the mRNAs of the mutants code for the synthesis of a polypeptide precursor characteristic of secreted proteins; the shortened proteins are apparently glycosylated intracellularly. Somatic cell hybrids between a structurally altered nonsecretor and a drug-marked wild-type myeloma cell secret only the wild-type protein. Reversion to secretion for G251 or I17 is accompanied by a change in the amino acid composition of the H chain such that gamma 2a subclass-specific determinants are expressed. Therefore, the primary structure of the H chain is an important factor in determining secretion. The gamma 2a-secreted chains from G251 and I17 fall into two classes: (1) those synthesizing proteins of approximately 47 000 daltons producing H-chain mRNAs of approximately 1.66 kilobases that are deleted for a portion, but not all, of CH1; (2) those synthesizing gamma2a proteins of approximately 55 000 daltons that are encoded in mRNAs of apparently wild-type size and that have regained CH1 sequences. The molecular explanations for the production of these alterations is discussed.

Animals↗
PubMed1970

Characterization of altered forms of glycyl transfer ribonucleic acid synthetase and the effects of such alterations on aminoacyl transfer ribonucleic acid synthesis in vivo.

The glycyl transfer ribonucleic acid (tRNA) synthetase (GRS) activities of several Escherichia coli glyS mutants have been partially characterized; the K(m) for glycine and the apparent V(max) of several of the altered GRS differ significantly from the parental GRS. Paradoxically, some of the altered forms exhibit more activity in vitro than the GRS from a prototrophic strain (GRS(L)); several parameters of these activities have been studied in an attempt to resolve this problem. The amount of acylated tRNA(Gly) in vivo was examined to assess the GRS activities inside the cells. During exponential growth in media containing glycine, moderate amounts of acylated tRNA(Gly) occur in the glyS mutants; glycine deprivation leads to a dramatic drop in the amount of acylated tRNA(Gly). An alternative measure of the in vivo activities of the altered enzymes is the efficiency of suppression of the trpA36 locus by su(36) (+); glyS mutants grown with added glycine exhibit one-third to one-fourth the suppression efficiency of the prototrophic glyS(H) parent, presumably because they are less efficient, even in the presence of high levels of glycine, in charging the tRNA(Gly) species which functions as the translational suppressor.

Amino Acids↗
PubMed1981

Effect of point mutations on 5.8S ribosomal ribonucleic acid secondary structure and the 5.8S--28S ribosomal ribonucleic acid junction.

Naturally occurring differences in the nucleotide sequences of 5.8S ribosomal ribonucleic acids (rRNAs) from a variety of organisms have been used to study the role of specific nucleotides in the secondary structure and intermolecular interactions of this RNA. Significant differences in the electrophoretic mobilities of free 5.8S RNAs and the thermal stabilities of 5.8S--28S rRNA complexes were observed even in such closely related sequences as those of man, rat, turtle, and chicken. A single base transition from a guanylic acid residue in position 2 in mammalian 5.8S rRNA to an adenylic acid residue in turtle and chicken 5.8S rRNA results both in a more open molecular conformation and in a 5.8S--28S rRNA junction which is 3.5 degrees C more stable to thermal denaturation. Other changes such as the deletion of single nucleotides from either the 5' or the 3' terminals have no detectable effect on these features. The results support secondary structure models for free 5.8S rRNA in which the termini interact to various degrees and 5.8S--28S rRNA junctions in which both termini of the 5.8S molecule interact with the cognate high molecular weight RNA component.

Alkaline Phosphatase↗
PubMed1973

Analysis of isoaccepting transfer ribonucleic acid species of Bacillus subtilis: changes in chromatography of transfer ribonucleic acids associated with stage of development.

Changes in chromatographic profiles of tyrosyl-, leucyl-, tryptophanyl-, and lysyl-transfer ribonucleic acids (tRNAs) are presented as a function of the growth stage in Bacillus subtilis. All of the tRNA groups investigated expressed different temporal patterns of change in isoaccepting species. Tyrosyl-tRNAs were the earliest to change and were followed by changes in leucyl- and then tryptophanyl-tRNAs. Lysyl-tRNAs were unique in having two times of change: one early and one very late. As an aid in understanding the temporal aspect of tRNA alterations during sporulation, the chromatographic profiles of aminoacyl tRNAs from an early blocked asporogenous mutant were studied. The asporogenous mutant used was blocked at the axial filament stage, stage 0 of sporulation. Nevertheless, those tRNAs which showed differences between the spore and cells in exponential growth exhibited similar changes in the asporogenous mutant after 24 h of growth. The data suggest that several tRNA changes occur during development in B. subtilis but that the events leading to these changes are either independent of, or occur before, stage 0 of sporulation, except in the case of lysyl-tRNA.

Amino Acyl-tRNA Synthetases↗
PubMed1971

Stimulation of ribonucleic acid synthesis by chloramphenicol in a rel + aminoacyl-transfer ribonucleic acid synthetase mutant of Escherichia coli.

Escherichia coli strain 9D3 possesses a highly temperature-sensitive valyl-transfer ribonucleic acid (tRNA) synthetase (EC 6.1.1.9). Since 9D3 is a rel(+) strain, it cannot carry out net RNA synthesis at high temperature. A 100-mug amount of chloramphenicol (CAP) per ml added in the absence of valine cannot stimulate RNA synthesis. Either 300 mug of CAP or 100 mug of CAP plus 50 mug of valine per ml, however, promotes nearly maximal RNA synthesis. These results can be understood as follows. (i) Valyl-tRNA is required for net RNA synthesis, (ii) the synthetase lesion is incomplete, (iii) the rate of mutant acylation of tRNA(val) at high temperature is valine-dependent, and (iv) the CAP concentration determines the rate of residual protein synthesis. Data are also presented which demonstrate that the rate of net RNA synthesis can greatly increase long after the addition of CAP, if the amount of valyl-tRNA increases.

Acylation↗
PubMed1980

Inhibition of ribonucleic acid accumulation in mouse L cells infected with vesicular stomatitis virus requires viral ribonucleic acid transcription.

The accumulation of ribonucleic acid (RNA) in mouse L-929 cells infected with temperature-sensitive mutants of vesicular stomatitis virus or ultraviolet- (UV-) irradiated virus was studied. At the permissive temperature (30 degrees C infection by all mutants resulted in an inhibition of cellular RNA accumulation. At the nonpermissive temperature (40 degrees C) mutants G114 (I) and G22 (II) failed to inhibit RNA accumulation, but mutants G11 (I), O52 (II), G31 (III), G33 (III), G41 (IV), W10 (IV), O45 (V), and O110 (V) were still active in this respect. In most cases the accumulation of 28S and 18S mature rRNA was inhibited to a greater extent than the synthesis of the 45S rRNA precursor. UV irradiation of wild type virus considerably reduced its capacity to inhibit cellular RNA synthesis. The target size for inactivation of this capacity of the virus was approximately 17% of the viral genome or that corresponding to the N gene. These results indicate that the virion proteins themselves are incapable of inhibiting cellular RNA synthesis and that transcription of approximately 17% of the genome is required. Expression of RNA synthesis inhibition also requires some function of virion NS protein in addition to its transcriptase activity.

Animals↗
PubMed1971

Characterization of mutants of Escherichia coli temperature-sensitive for ribonucleic acid regulation: an unusual phenotype associated with a phenylalanyl transfer ribonucleic acid synthetase mutant.

A mutant strain AA-522, temperature-sensitive for protein synthesis, was isolated from a stringent strain (CP-78) of Escherichia coli K-12. The mutant strain has a relaxed phenotype at the nonpermissive growth temperature. Protein synthesis stops completely at 42 C, whereas the rate of ribonucleic acid (RNA) synthesis is maintained at 20% of the 30 C rate. Sucrose-gradient centrifugation analysis of RNA-containing particles formed at 42 C indicated the presence of "relaxed particles." These particles possess 16S and 23S RNA and are precursors to normal 50S and 30S ribosomal subunits. A search for the temperature-sensitive protein responsible for the halt in protein synthesis implicated phenylalanyl transfer RNA (tRNA) synthetase. Essentially no enzyme activity is detected in vitro at 30 or 40 C. Analysis of phenylalanyl tRNA synthetase activity in revertants of strain AA-522 indicated the presence of intragenic suppressor mutations. Revertants of strain AA-522 analyzed for the relaxed response at 42 C were all stringent; strain AA-522 was stringent at 30 C. These data indicate that a single mutation in phenylalanyl tRNA synthetase is responsible for both a block in protein synthesis and the relaxed phenotype at 42 C.

Amino Acids↗
PubMed1976

Rapid micromethod for the purification of Escherichia coli ribonucleic acid polymerase and the preparation of bacterial extracts active in ribonucleic acid synthesis.

A rapid micromethod is described for the preparation of nucleic acid-free extracts from Escherichia coli that involves precipitation with polyethylene glycol. Extracts can be prepared from growing cells in 75 min by three short, low-speed centrifugations. The extract did not inhibit added purified ribonucleic acid (RNA) polymerase, suggesting that major inhibitors of RNA synthesis had been removed. This extract should be ideal for assessing the properties of mutant RNA polymerases. The rapid chromatography of the extracts with step elution from deoxyribonucleic acid- and diethylaminoethyl-cellulose columns resulted in high yields of substantially pure RNA polymerase. We used this technique to purify 35S-labeled RNA polymerase. This system should find application for the purification of small quantities of other bacterial RNA polymerases that share the general chromatographic properties of E. coli RNA polymerase.

Chemical Precipitation↗
PubMed1981

Ribonucleic acid synthesis termination protein rho function: effects of conditions that destabilize ribonucleic acid secondary structure.

The dependence fo rate of adenosine 5'-triphosphate (ATP) hydrolysis catalyzed by ribonucleic acid (RNA) synthesis termination protein rho from Escherichia coli with T7 RNA as cofactor is used to probe the nature of the interaction between rho and RNA. In general, reaction conditions that destabilize the secondary structure of the RNA enhance its cofactor activity. This is indicated by the effects of MgCl2 concentration, spermidine, temperature, dimethyl sulfoxide, and pretreatment of the RNA with formaldehyde. These results suggest that a functional interaction between rho and RNA depends either on the presence of a sufficiently large single-stranded region in the RNA or on the ability of rho to unwind double helices in the RNA. It is also shown that changes in reaction conditions that increase RNA secondary structure and decrease the rho protein adenosine triphosphate phosphohydrolase (rhoATPase) activity with isolated T7 RNA also decrease the stringency of rho action in RNA synthesis termination. On the other hand, monovalent salts decrease rhoATPase activity with isolated T7 RNA and binding of rho to T7 RNA independently of the MgCl2 concentration and thus the relative stability of the RNA secondary structure.

DNA-Directed RNA Polymerases↗