Degradation Of Ribosomal RNA Research Articles

Effects of two TMV strains on the synthesis and stability of chloroplast ribosomal RNA in tobacco leaves.

Multiplication of TMV-strains vulgare (light-green/dark-green mosaic symptoms) and flavum (severe yellow/green mosaic) had different effects on the ribosomal RNA of tobacco leaf chloroplasts. Vulgare inhibited chloroplast ribosomal RNA synthesis while having no effect on cytoplasmic ribosomal RNA synthesis (Fig. 2). Flavum inhibited chloroplast ribosomal RNA synthesis more severely than vulgare, and caused an earlier degradation of chloroplast ribosomal RNA than in control or vulgare-infected leaves (Fig. 1). Flavum also inhibited cytoplasmic ribosomal RNA synthesis. A connection between these differing effects on chloroplast ribosomal RNA metabolism and severity of visible symptoms is suggested, and discussed in relation to a possible influence on symptoms of denatured virus coat protein.

Turnover of ribosomal RNA in a ribonuclease I-less mutant of Escherichia coli, Q-13, which was found to possess polynucleotide phosphorylase

1. 1. A completely synthetic medium was found for Escherichia coli Q-13 (ribonuclease I-less mutant), containing methionine, tryptophan, tyrosine and leucine. 2. 2. Ribosomal RNA degradation was observed in Q-13 in phosphate- and magnesium-deficient states. All the patterns coincided well with those in the wild type of E. coli. 3. 3. When pulse-labelled with [ 14C]uracil, RNA gave [ 14C] UDP and [ 14C]UMP as degradation products in the presence of Na 2HPO 4. When labelling with [ 14C]adenine was used, a very small amount of [ 14C]ADP was detected among the degradation products. 4. 4. E. coli Q-13 contains higher nucleoside diphosphate pyrophosphatase activity than the wild strain. Evidence is given that it masked the polynucleotide phosphorylase (EC 2.7.7.8) actually present in E. coli Q-13. 5. 5. It is proposed that the enzymes responsible for the degradation of ribosomal RNA and messenger RNA are polynucleotide phosphorylase and ribonuclease II (EC 3.1.4.1.) in both the wild and mutant strains used.

Absence of ribonuclease in Alcaligenes faecalis and a possible mechanism of RNA degradation in this bacterium

1. Alcaligenes faecalis RN-4 was shown to have no detectable intra- or extracellular ribonuclease I (EC 2.7.7.16) activity. In this strain, ribosomal and messenger RNA's were degraded by polynucleotide phosphorylase (EC 2.7.7.8) and potassium-activated phosphodiesterase (EC 3.1.4.1) in vitro as demonstrated by the detection of nucleoside diphosphates and 5′-nucleotides as degradation products. 2. Mitomycin C induced the degradation of the ribosomal RNA of A. faecalis RN-4 in the same way as in Escherichia coli which is known to have a ribonuclease I. 3. In view of these results, the possibility that the ribonuclease I in Escherichia coli does not actually participate in the degradation of ribosomal RNA is discussed.

Degradation of ribosomal RNA from Escherichia coli induced by colicine E2

Degradation of ribosomal RNA from Escherichia coli induced by colicine E2

The turnover of ribosomal RNA of Escherichia coli in a magnesium-deficient stage

1. 1. Escherichia coli was grown in a magnesium-deficient medium. The ribosomal RNA was labeled, and followed during separation by chromatography on methylated bovine serum albumin. Marked degradation of ribosomal RNA was observed, although the total amount remained constant. This means that there was a rapid turnover of ribosomal RNA during growth. 2. The degradation products of ribosomal RNA during magnesium deficiency first appeared in the region of soluble RNA on methylated bovine serum albumin chromatograms, but were later released into the culture medium. 3. When pulse labeled with 32P in the magnesium-deficient stage, no DNA-type RNA was obtained, but heterogeneous RNA's appeared with nucleotide compositions of the ribosomal RNA type. These RNA's were presumed to be precursors of ribosomal RNA.

The participation of ribonuclease in the degradation of Escherichia coli ribosomal ribonucleic acid as revealed by oligonucleotides accumulation in the phosphorus-deficient stage

1. 1. Escherichia coli ribosomal RNA degradation during the phosphorus-deficient stage 1,2 was investigated by analysis of its degradation products. 2. 2. After exhaustion of the phosphorus in the medium, 32P in the 50 % ethanolsoluble fraction of the bacterial cell increased greatly in parallel with the degradation of ribosomal RNA, while trichloroacetic acid-soluble 32P did not. 3. 3. Soon after phosphorus exhaustion, most of the ethanol-soluble 32P consisted of characteristic oligonucleotides. Later, inorganic phosphate increased gradually parallel with a decrease in oligonucleotides in ethanol extracts. 4. 4. The differences in the base ratios, the terminal structures and other properties of these oligonucleotides suggest that the breakdown of ribosomal RNA was caused mainly by ribosomal latent ribonuclease (EC 2.7.7.17) 3. These oligonucleotides, in their turn, were found to be finally converted to inorganic phosphate and nucleosides by the cooperation of alkaline phosphomonoesterase (EC 3.1.3.1) 2,4 and cyclic phosphodiesterase 5,6.

Ribonuclease Levels in the Mesocotyl Tissue of Zea mays as a Function of 2,4-Dichlorophenoxyacetic Acid Application

The application of high concentrations of 2,4dichlorophenoxyacetic acid (2,4-D) to plants results in increased nucleic acid content (4, 11, 17, 22). The RNA synthesized is largely ribosomal (4, 13). Since IAA will also induce increases in nucleic acids (6, 19) the auxin properties of 2,4-D are presumably involved. If basal stem tissues of soybean (13) or corn (22) seedlings are incubated with appropriate concentrations of 2,4-D a net synthesis of RNA can be obtained. With apical tissues this does not occur. High concentrations of the auxin prevent the degradation of ribosomal and soluble RNA that normally accompany the expansive growth of young cells but no synthesis is involved (9). A factor of unknown significance in this auxin-mediated RNA metabolism is ribonuclease(s) (RNase). There have been suggestions that RNases may have synthetic functions in plants (2, 8, 14). As cells expand there is an increase in RNase activity (3,6,8,18); possibly the high RNase levels of older cells have something to do with the RNA synthesis enhanced by 2,4-D application. On the other hand, if RNases have solely degradative functions, high concentrations of 2,4-D may block RNA degradation by inhibiting the enzymes or suppressing RNase synthesis. It appeared to us that studies on the level of RNase as a function of 2,4-D application were needed. This paper reports our findings from such an investigation.