scholarly journals METABOLISM OF RIBOSOMAL PRECURSOR RIBONUCLEIC ACID IN KIDNEY

1970 ◽  
Vol 46 (2) ◽  
pp. 362-369 ◽  
Author(s):  
Geert Ab ◽  
Ronald A. Malt
Keyword(s):  
Ribosomal Rna ◽  
Intermediate Product ◽  
Turnover Time ◽  
Mouse Kidney ◽  
Rnase Inhibitor ◽  
Phenol Extraction ◽  
Precursor Rna ◽  
Ribosomal Precursor ◽  
Kinetics Of ◽  
Rna Precursor

The labile precursors of ribosomal RNA in mouse kidney are preserved when nuclei rapidly isolated after sieving through multiple screens are swollen and cleansed in the presence of an RNase inhibitor before digestion with DNase and phenol extraction. The kinetics of nucleolar labeling analyzed on polyacrylamide gels show that 36S RNA is the major intermediate product in the catabolism of the original 45S RNA precursor to 32S RNA, from which 28S RNA is derived. Each kidney nucleus contains about 200–600 molecules of 45S RNA; the turnover time of the 45S pool is about 3 ± 2 min. Compared with HeLa cells, kidney nuclei have a different major intermediate product and a much smaller and more rapidly turning-over pool of ribosomal precursor RNA.

scholarly journals Assembly of 5S Ribosomal RNA Is Required at a Specific Step of the Pre-rRNA Processing Pathway

1999 ◽  
Vol 145 (7) ◽  
pp. 1369-1380 ◽  
Author(s):  
Anne-Marie Dechampesme ◽  
Olga Koroleva ◽  
Isabelle Leger-Silvestre ◽  
Nicole Gas ◽  
Sylvie Camier
Keyword(s):  
Ribosomal Rna ◽  
5S Rna ◽  
Nucleolar Structure ◽  
Yeast Strains ◽  
5.8S Rrna ◽  
Specific Step ◽  
Mutant Strains ◽  
Efficient Processing ◽  
Precursor Rna ◽  
Rna Precursor

A collection of yeast strains surviving with mutant 5S RNA has been constructed. The mutant strains presented alterations of the nucleolar structure, with less granular component, and a delocalization of the 25S rRNA throughout the nucleoplasm. The 5S RNA mutations affected helix I and resulted in decreased amounts of stable 5S RNA and of the ribosomal 60S subunits. The shortage of 60S subunits was due to a specific defect in the processing of the 27SB precursor RNA that gives rise to the mature 25S and 5.8S rRNA. The processing rate of the 27SB pre-rRNA was specifically delayed, whereas the 27SA and 20S pre-rRNA were processed at a normal rate. The defect was partially corrected by increasing the amount of mutant 5S RNA. We propose that the 5S RNA is recruited by the pre-60S particle and that its recruitment is necessary for the efficient processing of the 27SB RNA precursor. Such a mechanism could ensure that all newly formed mature 60S subunits contain stoichiometric amounts of the three rRNA components.

scholarly journals THE EFFECT OF PUROMYCIN ON INTRANUCLEAR STEPS IN RIBOSOME BIOSYNTHESIS

1968 ◽  
Vol 36 (1) ◽  
pp. 91-101 ◽  
Author(s):  
R. Soeiro ◽  
M. H. Vaughan ◽  
J. E. Darnell
Keyword(s):  
Protein Synthesis ◽  
Ribosomal Rna ◽  
Cell Fractionation ◽  
Sequence Of Events ◽  
Inhibition Of Protein Synthesis ◽  
Precursor Rna ◽  
Initial Processing ◽  
Inhibitor Of Protein Synthesis ◽  
Ribosomal Precursor ◽  
Ribosome Biosynthesis

Inhibition of protein synthesis by puromycin (100 γ/ml) is known to inhibit the synthesis of ribosomes. However, ribosomal precursor RNA (45S) continues to be synthesized, methylated, and processed. Cell fractionation studies revealed that, although the initial processing (45S → 32S + 16S) occurs in the presence of puromycin, the 16S moiety is immediately degraded. No species of ribosomal RNA can be found to have emerged from the nucleolus. The RNA formed in the presence of puromycin is normal as judged by its ability to enter new ribosomal particles after puromycin is removed. This sequence of events is not a result of inhibition of protein synthesis, for cycloheximide, another inhibitor of protein synthesis, either alone or in combination with puromycin allows the completion of new ribosomes.

The kinetics of hydration of tricalcium silicate

1970 ◽  
Vol 48 (21) ◽  
pp. 3291-3299 ◽  
Author(s):  
K. G. McCurdy ◽  
B. P. Erno
Keyword(s):  
Reaction Mechanism ◽  
Intermediate Product ◽  
Activation Energies ◽  
Tricalcium Silicate ◽  
Rate Data ◽  
Large Excess ◽  
First Order ◽  
Kinetics Of ◽  
Subsequent Decomposition

An investigation has been made of the kinetics of hydration of tricalcium silicate at several temperatures in a large excess of water in the presence of various added ions. The rate data have been interpreted by a reaction mechanism which involves: (a) the first order hydration of tricalcium silicate to form an intermediate product, 1.5CaO•SiO2, which can react by two pathways, (b) the direct first order decomposition of intermediate, 1.5CaO•SiO2, to form lime and silica or (b′) complexing of intermediate with silica and subsequent decomposition to form lime and silica. This reaction mechanism predicts the rate of production of base during the hydration. The effect of various added ions is interpreted in terms of the proposed mechanism.Rate constants and activation energies for the various steps in the proposed mechanism are reported.

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