The kinetics of product appearance and template involvement in the in vitro replication of viral RNA

Escherichia coli traD(Ts) mutant temperature sensitive for assembly of RNA bacteriophage MS2

We report here a study on the temperature-sensitive conjugational transfer-deficient mutant Escherichia coli JCFL39, carrying a traD(Ts) mutation, which is also temperature sensitive for group I RNA phages (MS2, f2, and R17). It is shown that, when the mutant was infected with MS2 at 42 degrees C, phage RNA replicated; a 27S MS2 RNA and phage proteins were synthesized. However, neither PFU nor physical MS2 particles were formed, showing that phage assembly was inhibited. In addition, the high temperature affected the membranes of the host mutant: the mutant was hypersensitive to chemicals, and the electrophoretic pattern of the membranal proteins was modified. We suggest that the pleiotropic effects of the traD mutation on MS2 assembly and DNA transfer during conjugation were a result of the changes in the membrane of the mutant.

Transfection of Enterobacteriaceae and its applications

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Discriminative effect of rifampin of RNA replication of various RNA bacteriophages

Rifampin interferes exclusively with RNA replication in vivo of the group I phages MS2, f2, and R17, whereas QbetaRNA replication is unaffected by the drug. In addition, rifampin has a discriminative effect of group I phage RNA replication. In the experimental system employed by us the antibiotic differentially interferes with the synthesis of minus RNA strands in f2, whereas it has almost no effect on the synthesis of progeny plus strands. In MS2, the drug differentially arrests the synthesis of progeny plus strands and almost fails to affect the synthesis of minus RNA strands. In R17 both steps of its RNA replication are affected by rifampin, although each step is only partially (approximately 50%) inhibited. The relation of the present results to the possible role of bacterial proteins and tertiary structure of phage RNA in the process of template recognition is discussed.

The 7S RNA common to oncornaviruses and normal cells is associated with polyribosomes

The 7S RNA species first demonstrated in avian and murine oncornaviruses and later in normal, uninfected cells is found associated in part with cellular polyribosomes. A molar ratio of 7S RNA to 5S ribosomal RNA of 0.05 indicates that there is approximately one mole of 7S RNA per mole of messenger RNA. Dissociation of polyribosomes with dimethylsulfoxide results in a marked decrease in the sedimentation rate of the 7S RNA. The dimethylsulfoxide-induced dissociation of polyribosomes and the concomitant movement of the 7S RNA from the polyribosome region into lighter regions of a sucrose gradient are both inhibited by cycloheximide, indicating that the 7S RNA is indeed associated with polyribosomes and not with a ribonucleoprotein particle sedimenting with polyribosomes.

A replicating RNA molecule suitable for a detailed analysis of extracellular evolution and replication

The aim of the present study is to make available a replicating molecule of known sequence. Accordingly, we sought a molecule that has the following properties: (a) replicates in vitro in a manner similar to phage Qbeta RNA; (b) produces antiparallel complementary strands that can be separated from one another; and (c) is small enough to yield its sequence with reasonable effort. We report here the isolation of a replicating RNA molecule that contains 218 nucleotides and possesses the other features desired for a definitive analysis of the replicating mechanism. Despite its small size, this molecule can mutate to previously determined phenotypes. It will, therefore, permit the precise identification of the base changes required to mutate from one phenotype to another in the course of extracellular Darwinian selection experiments.

Polysomal localization of R17 bacteriophage-specific protein synthesis

Synthesis of viral ribonucleic acid (RNA) polymerase, maturation protein, and coat protein in Escherichia coli infected with bacteriophage R17 occurs mainly on polysomes containing four or more ribosomes. The 30S ribosomal subunits through trimer-size polysomes, which are associated with all of the R17-specific proteins and are predominant in the infected cell, synthesize only coat protein. These structures may accumulate as products derived from larger polysomes as a result of failure in the release of nascent polypeptides after termination of chain growth. Appreciable amounts of viral coat protein remain attached to ribosomes and polysomes during R17 bacteriophage replication, supporting the hypothesis of the repressor role of this protein. The time course of synthesis of virus-specific proteins obtained from the polysomes of infected cells demonstrated regulated R17 messenger RNA translation consistent with the idea that coat protein is preferentially synthesized whereas the synthesis of noncoat proteins is suppressed.

Ribonucleic acid synthesis in bacteria treated with toluene

Escherichia coli and Bacillus megaterium rendered permeable to ribonucleoside triphosphates by toluene treatment retain the capacity to synthesize discrete ribonucleic acid species.

Transcriptional organization of the ribosomal RNA cistrons in Escherichia coli

The data presented support the hypothesis that 16S, 23S, and 5S ribosomal RNAs of Escherichia coli are transcribed in vivo from transcriptional units consisting of single cistrons for these species arranged in the order 16S-23S-5S, with transcription beginning at the 16S end.

Formation of all stable RNA species in Escherichia coli by posttranscriptional modification

The kinetics of accumulation of the known stable RNA species (23S, 16S, and 5S rRNA and tRNA) in Escherichia coli C122 were monitored by polyacrylamide gel electrophoresis of purified cellular RNA, following termination of brief pulse labeling with (32)P-orthophosphate. Isotopically labeled stable RNA species appear only after a time lag, while total cellular RNA and the ostensible precursors to the stable RNA classes accumulate from the earliest times examined. It is concluded that all the known stable RNA species in E. coli are the products of posttranscriptional modification.

In vitro synthesis of poliovirus ribonucleic acid: role of the replicative intermediate

Poliovirus ribonucleic acid (RNA) polymerase crude extracts could be stored frozen in liquid nitrogen without loss of activity or specificity. The major in vitro product of these extracts was viral single-stranded RNA. However, after short periods of incubation with radioactive nucleoside triphosphates, most of the incorporated label was found in replicative intermediate. When excess unlabeled nucleoside triphosphate was added, the label was displaced from the replicative intermediate and accumulated as viral RNA. It is concluded from this experiment that the replicative intermediate is the precursor to viral RNA. In addition, some of the label was chased into double-stranded RNA. The implications of this finding are discussed.

Replication of bacteriophage ribonucleic acid: analysis of the ultrastructure of the replicative form and the replicative intermediate of bacteriophage R17

A detailed qualitative and quantitative comparison was made of the ultrastructure of single-stranded ribonucleic acid (RNA) from bacteriophage R17 and double-stranded replicative form (RF) and replicative intermediate (RI) from cells infected with this bacteriophage. The nucleic acids were prepared for electron microscopy by the protein monolayer spreading technique of Kleinschmidt. Single-stranded RNA aggregated during spreading in the absence of urea, whereas RF and RI did not. On the other hand, RF and RI appeared to be susceptible to shear during spreading, whereas R17 RNA was not. From the maximal length of RF, a base translation of 3.14 A was calculated. This value favors a 10-fold helix model of double-stranded RNA. The same base translation was found for R17 RNA, indicating a stacked base structure for single-stranded RNA spread in the presence of urea. RI is a branched structure and the branches are removed by ribonuclease treatment. The branches are believed to be nascent single-stranded viral RNA. The contour length of the branch was equal to the contour length of the main chain up to the branch point, as predicted from theoretical analysis of the replication of viral RNA. The structure of RF and the main chain of RI was also analyzed by plotting the log (end-to-end distance squared) versus log (contour length). This demonstrated structures intermediate in stiffness between a random coil and a rigid rod.