scholarly journals Post-transcriptional regulation of ribosome formation in the nucleus of regenerating rat liver

1983 ◽  
Vol 210 (1) ◽  
pp. 183-192 ◽  
Author(s):  
K P Dudov ◽  
M D Dabeva
Keyword(s):  
Rat Liver ◽  
Ribosome Biogenesis ◽  
Rrna Processing ◽  
Regenerating Liver ◽  
Regenerating Rat Liver ◽  
Rrna Species ◽  
Rrna Maturation ◽  
The Individual ◽  
Post Transcriptional Regulation

Kinetic experiments on RNA labelling in vivo with [14C]orotate were performed with normal and 12h-regenerating rat liver. The specific radioactivities of nucleolar, nucleoplasmic and cytoplasmic rRNA species were analysed by computer according to the models of rRNA processing and nucleo-cytoplasmic migration given previously [Dudov, Dabeva, Hadjiolov & Todorov, Biochem. J. (1978) 171, 375-383]. The rates of formation and the half-lives of the individual pre-rRNA and rRNA species were determined in both normal and regenerating liver. The results show clearly that the formation of ribosomes in regenerating rat liver is post-transcriptionally activated: (a) the half-lives of all the nucleolar pre-rRNA and rRNA species are decreased by 30% on average; (b) the pre-rRNA processing is directed through the shortest maturation pathway: 45 S leads to 32 S + 18 S leads to 28 S; (c) the nucleo-cytoplasmic transfer of ribosomes is accelerated. As a consequence, the time for formation and appearance of ribosomes in the cytoplasm is shortened 1.5-fold for the large and 2-fold for the small subparticle. A new scheme for endonuclease cleavage of 45 S pre-rRNA is proposed, which explains the alterations in pre-rRNA processing in regenerating liver. Its validity for pre-rRNA processing in other eukaryotes is discussed. It is concluded that: (i) the control sites in the intranucleolar formation of 28 S and 18 S rRNA are the immediate precursor of 28 S rRNA, 32 S pre-rRNA, and the primary pre-rRNA, 45 S pre-rRNA, respectively; (ii) the limiting step in the post-transcriptional stages of ribosome biogenesis is the pre-rRNA maturation.

scholarly journals Quantitative alterations in the nucleolar and nucleoplasmic ribosomal ribonucleic acids in regenerating rat liver

1982 ◽  
Vol 204 (1) ◽  
pp. 179-183 ◽  
Author(s):  
Mariana D. Dabeva ◽  
Kalin P. Dudov
Keyword(s):  
Quantitative Analysis ◽  
Rat Liver ◽  
Rrna Processing ◽  
Regenerating Liver ◽  
Ribonucleic Acids ◽  
Regenerating Rat Liver ◽  
Rrna Species ◽  
The Absolute ◽  
Pool Sizes

A quantitative analysis of the nuclear pre-rRNA (precursor to rRNA) and rRNA in normal and 12h-regenerating rat liver was carried out, and the absolute amounts of the identified pre-rRNA and rRNA species in the nucleolus and nucleoplasm were determined. Characteristic changes in the pre-rRNA and rRNA pool sizes in regenerating liver are found which reveal alternations in both pre-rRNA processing and nucleocytoplasmic transition of ribosomes.

DEOXYCYTIDYLATE DEAMINASE LEVELS IN REGENERATING RAT LIVER

1961 ◽  
Vol 39 (6) ◽  
pp. 1043-1054 ◽  
Author(s):  
D. K. Myers ◽  
C. Anne Hemphill ◽  
Constance M. Townsend
Keyword(s):  
Dna Synthesis ◽  
Liver Regeneration ◽  
Partial Hepatectomy ◽  
Rat Liver ◽  
Deoxyribonucleic Acid ◽  
Regenerating Liver ◽  
Regenerating Rat Liver ◽  
High Level ◽  
Early Regeneration

Deoxycytidylate deaminase activity and net synthesis of deoxyribonucleic acid (DNA) in vivo were found to increase at approximately the same time during the early stages of liver regeneration. However, deaminase activity in the regenerating liver remained at a high level for 1 day after DNA synthesis had slowed down again during the later stages of regeneration. The increase in deaminase activity was restricted as a result of exposure to 600 r X radiation during early regeneration, but this effect only became evident 11–16 hours after the irradiation. Irradiation on the second day after partial hepatectomy, when deaminase levels in control regenerating livers were relatively constant, failed to affect the deaminase activity immediately but did produce a 40–50% decrease in activity 11–16 hours later. Other antimitotic agents, e.g., colchicine, had little effect on deaminase activity.

scholarly journals The Putative NTPase Fap7 Mediates Cytoplasmic 20S Pre-rRNA Processing through a Direct Interaction with Rps14

2005 ◽  
Vol 25 (23) ◽  
pp. 10352-10364 ◽  
Author(s):  
Sander Granneman ◽  
Madhusudan R. Nandineni ◽  
Susan J. Baserga
Keyword(s):  
High Throughput ◽  
Structural Component ◽  
Ribosome Biogenesis ◽  
18S Rrna ◽  
Direct Interaction ◽  
Nucleoside Triphosphate ◽  
Rrna Processing ◽  
Conserved Residues ◽  
Rrna Maturation

ABSTRACT One of the proteins identified as being involved in ribosome biogenesis by high-throughput studies, a putative P-loop-type kinase termed Fap7 (YDL166c), was shown to be required for the conversion of 20S pre-rRNA to 18S rRNA. However, the mechanism underlying this function has remained unclear. Here we demonstrate that Fap7 is strictly required for cleavage of the 20S pre-rRNA at site D in the cytoplasm. Genetic depletion of Fap7 causes accumulation of only the 20S pre-rRNA, which could be detected not only in 43S preribosomes but also in 80S-sized complexes. Fap7 is not a structural component of 43S preribosomes but likely transiently interacts with them by directly binding to Rps14, a ribosomal protein that is found near the 3′ end of the 18S rRNA. Consistent with an NTPase activity, conserved residues predicted to be required for nucleoside triphosphate (NTP) hydrolysis are essential for Fap7 function in vivo. We propose that Fap7 mediates cleavage of the 20S pre-rRNA at site D by directly interacting with Rps14 and speculate that it is an enzyme that functions as an NTP-dependent molecular switch in 18S rRNA maturation.

scholarly journals The sequence of the 5' end of the U8 small nucleolar RNA is critical for 5.8S and 28S rRNA maturation.

1997 ◽  
Vol 17 (7) ◽  
pp. 3702-3713 ◽  
Author(s):  
B A Peculis
Keyword(s):  
Ribosome Biogenesis ◽  
Critical Role ◽  
Functional Site ◽  
28S Rrna ◽  
Rrna Processing ◽  
Hybrid Molecules ◽  
Evolutionarily Conserved ◽  
Rrna Maturation ◽  
Base Pairing Interaction

Ribosome biogenesis in eucaryotes involves many small nucleolar ribonucleoprotein particles (snoRNP), a few of which are essential for processing pre-rRNA. Previously, U8 snoRNA was shown to play a critical role in pre-rRNA processing, being essential for accumulation of mature 28S and 5.8S rRNAs. Here, evidence which identifies a functional site of interaction on the U8 RNA is presented. RNAs with mutations, insertions, or deletions within the 5'-most 15 nucleotides of U8 do not function in pre-rRNA processing. In vivo competitions in Xenopus oocytes with 2'O-methyl oligoribonucleotides have confirmed this region as a functional site of a base-pairing interaction. Cross-species hybrid molecules of U8 RNA show that this region of the U8 snoRNP is necessary for processing of pre-rRNA but not sufficient to direct efficient cleavage of the pre-rRNA substrate; the structure or proteins comprising, or recruited by, the U8 snoRNP modulate the efficiency of cleavage. Intriguingly, these 15 nucleotides have the potential to base pair with the 5' end of 28S rRNA in a region where, in the mature ribosome, the 5' end of 28S interacts with the 3' end of 5.8S. The 28S-5.8S interaction is evolutionarily conserved and critical for pre-rRNA processing in Xenopus laevis. Taken together these data strongly suggest that the 5' end of U8 RNA has the potential to bind pre-rRNA and in so doing, may regulate or alter the pre-rRNA folding pathway. The rest of the U8 particle may then facilitate cleavage or recruitment of other factors which are essential for pre-rRNA processing.

scholarly journals Comprehensive Mutational Analysis of Yeast DEXD/H Box RNA Helicases Required for Small Ribosomal Subunit Synthesis

2006 ◽  
Vol 26 (4) ◽  
pp. 1183-1194 ◽  
Author(s):  
Sander Granneman ◽  
Kara A. Bernstein ◽  
Franziska Bleichert ◽  
Susan J. Baserga
Keyword(s):  
Ribosome Biogenesis ◽  
Mutational Analysis ◽  
Ribosomal Subunit ◽  
Biochemical Properties ◽  
Dominant Negative ◽  
Rrna Synthesis ◽  
Rrna Processing ◽  
Rna Helicases ◽  
Rrna Species

ABSTRACT The 17 putative RNA helicases required for pre-rRNA processing are predicted to play a crucial role in ribosome biogenesis by driving structural rearrangements within preribosomes. To better understand the function of these proteins, we have generated a battery of mutations in five putative RNA helicases involved in 18S rRNA synthesis and analyzed their effects on cell growth and pre-rRNA processing. Our results define functionally important residues within conserved motifs and demonstrate that lethal mutations in predicted ATP binding-hydrolysis motifs often confer a dominant negative phenotype in vivo when overexpressed in a wild-type background. We show that dominant negative mutants delay processing of the 35S pre-rRNA and cause accumulation of pre-rRNA species that normally have low steady-state levels. Our combined results establish that not all conserved domains function identically in each protein, suggesting that the RNA helicases may have distinct biochemical properties and diverse roles in ribosome biogenesis.

Inhibition of in vivo DNA synthesis in regenerating rat liver following thermal injury

1989 ◽  
Vol 160 (1) ◽  
pp. 196-201 ◽  
Author(s):  
Edward A. Carter ◽  
Sara E. Kirkham ◽  
Ronald G. Tompkins ◽  
John F. Burke
Keyword(s):  
Dna Synthesis ◽  
Rat Liver ◽  
Thermal Injury ◽  
Regenerating Rat Liver

scholarly journals Thymidine metabolism in regenerating rat liver one to two hours after partial hepatectomy

1973 ◽  
Vol 136 (3) ◽  
pp. 571-577 ◽  
Author(s):  
Margery G. Ord ◽  
Lloyd A. Stocken
Keyword(s):  
Partial Hepatectomy ◽  
Intravenous Injection ◽  
Rat Liver ◽  
Thymidine Uptake ◽  
Regenerating Rat Liver ◽  
Perfusion Studies ◽  
Saturation Kinetics

1. When [3H]thymidine was injected intravenously into rats in amounts up to 40mg/kg body wt. and the3H radioactivity in the livers measured at 30min, saturation kinetics for thymidine uptake were not found. If the animals were examined 3 min after intravenous injection, saturation could be attained in normal rats with 12mg of thymidine/kg and in partially hepatectomized rats with 4mg/kg. At concentrations of thymidine close to saturation, no differences were found in rate or amount of uptake/g of liver between normal and partially hepatectomized rats 1–2h after operation. 2. Perfusion techniques were used to compare thymidine uptakes in the two sets of rats at concentrations up to 40μm-thymidine. Uptakes with tracer amounts of thymidine after 30min were identical in vivo and in the perfusion studies and were twice as great in livers from partially hepatectomized rats with concentrations up to 40μm-thymidine. 3. At 1.5h after operation there was nearly twice as much β-aminoisobutyrate present per g of liver from partially hepatectomized as compared with normal rats.

scholarly journals Intranuclear maturation pathways of rat liver ribosomal ribonucleic acids

1976 ◽  
Vol 160 (3) ◽  
pp. 495-503 ◽  
Author(s):  
M D Dabeva ◽  
K P Dudov ◽  
A A Hadjiolov ◽  
I Emanuilov ◽  
B N Todorov
Keyword(s):  
Secondary Structure ◽  
Rat Liver ◽  
Mammalian Cells ◽  
18S Rrna ◽  
Electron Microscopic Observation ◽  
28S Rrna ◽  
Electron Microscopic ◽  
Rrna Species ◽  
A Minor

The maturation of pre-rRNA (precursor to rRNA)in liver nuclei is studied by agar/ureagel electrophoresis, kinetics of labelling in vivo with [14C] orotate and electron-microscopic observation of secondary structure of RNA molecules. (1) Processing starts from primary pre-rRNA molecules with average mol. wt. 4.6×10(6)(45S) containing the segments of both 28S and 18S rRNA. These molecules form a heterogeneous peak on electrophoresis. The 28S rRNA segment is homogeneous in its secondary structure. However, the large transcribed spacer segment (presumably at the 5′-end) is heterogeneous in size and secondary structure. A minor early labelled RNA component with mol.wt. about 5.8×10(6) is reproducibly found, but its role as a pre-rRNA species remains to be determined. (2) The following intermediate pre-rRNA species are identified: 3.25×10(6) mol.wt.(41S), a precursor common to both mature rRNA species; 2.60×10(6)(36S) and 2.15×10(6)(32S) precursors to 28S rRNA; 1.05×10(6) (21S) precursor to 18S rRNA. The pre-rRNA molecules in rat liver are identical in size and secondary structure with those observed in other mammalian cells. These results suggest that the endonuclease-cleavage sites along the pre-rRNA chain are identical in all mammalian cells. (3) Labelling kinetics and the simultaneous existence of both 36S and 21S pre-rRNA reveal that processing of primary pre-rRNA in adult rat liver occurs simultaneously by at least two major pathways: (i) 45S → 41S → 32S+21S → 28S+18S rRNA and (ii) 45S → 41S → 36S+18S → 32S → 28S rRNA. The two pathways differ by the temporal sequence of endonuclease attack along the 41 S pre-rRNA chain. A minor fraction (mol.wt.2.9×10(6), 39S) is identified as most likely originating by a direct split of 28S rRNA from 45S pre-rRNA. These results show that in liver considerable flexibility exists in the order of cleavage of pre-rRNA molecules during processing.

Alterations in Deoxyribonucleic Acid from Regenerating Rat Liver after X-radiation in vivo

Nature ◽  
1962 ◽  
Vol 194 (4831) ◽  
pp. 883-884 ◽  
Author(s):  
R. FOSTER ◽  
MARGERY G. ORD
Keyword(s):  
Rat Liver ◽  
Deoxyribonucleic Acid ◽  
Regenerating Rat Liver
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