Free ribosomes during maturation of rat liver

Oliver, I.T.; Blumer, W.; Witham, I.J.

doi:10.1016/0010-406x(63)90100-2

Cited by 59 publications

(32 citation statements)

References 8 publications

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“…The apparent twofold decrease in the steady-state level of rRNA between fetal and adult liver is consistent with a previous estimation based on an analytical ultracentrifugation of free ribosomes (59). This change is comparable with the two-to threefold increase in cellular content of ribosomes, observed during transitions between resting and growing states of cells in culture (9,33,71), which results from a combination of two or more mechanisms operating in different cell lines and under various growth conditions.…”

Section: Discussionsupporting

confidence: 90%

Selective translational control and nonspecific posttranscriptional regulation of ribosomal protein gene expression during development and regeneration of rat liver.

Aloni¹,

Peleg²,

Meyuhas³

1992

Mol. Cell. Biol.

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Mammalian liver development is accompanied by a transition from rapid growth in the fetus to a quiescent state in the adult. However, extensive proliferation can be induced in the adult liver by partial hepatectomy. In this study, we examined the regulation of ribosomal protein (rp) gene expression in the developing and regenerating rat liver. Our results indicate that the translation of rp mRNAs is selectively repressed by about 70%o upon development from fetal to adult life, as illustrated by the decrease in ribosomal loading. In addition, the relative abundance of these mRNAs, like that of several other, but not all, housekeeping mRNAs, declines during development through a posttranscriptional mechanism. When liver cells commence growth following partial hepatectomy, translation of rp mRNAs is resumed to near-maximal capacity, as judged by their very efficient recruitment into polysomes. The concomitant increase in the abundance of rp mRNAs under these circumstances is achieved by a posttranscriptional mechanism. The apparent fluctuations in the translation efficiency of rp mRNAs are accompanied by parallel changes in the expression of the genes encoding the initiation factors eIF-4E and eIF-4A. Our results indicate that selective translational control of rp mRNAs in mammals is not confined to manipulated cells in culture but constitutes an important regulatory mechanism operating in vivo in the course of liver development and regeneration.The biosynthesis of ribosomes in vertebrates is primarily coordinated with the cellular growth status and requires an equimolar accumulation of four rRNA and about 80 different ribosomal protein (rp) molecules. This stoichiometry is maintained by coordinate regulation at various levels of gene expression from transcription to protein turnover (4,31,43,49). Clearly, the translational control of rp mRNAs is the most prevalent regulatory mechanism of vertebrate rp gene expression and operates under a variety of physiological conditions (reference 41 and references therein). Recently, we have shown that the 5'-terminal pyrimidine tract, adjacent to the cap site of all vertebrate rp mRNAs rigorously analyzed thus far, plays a critical role in their coordinate translational control (41).Posttranscriptional control of rp genes, most probably through stability of the corresponding transcripts, has been reported to occur in anucleate Xenopus embryos (62) and in dexamethasone-treated rats (21). In addition, control at the RNA processing level is evident for rpL1 in Xenopus laevis (10). Finally, a balanced accumulation of ribosomal proteins (r-proteins) is also achieved by modulating their turnover, as observed in mouse oocytes (39) and differentiating rat myoblasts (30).The development of rodent liver is associated with progressive decrease of mitotic activity to almost undetectable levels in the adult tissue (reference 46 and references therein). Concomitantly, the hepatocytes acquire differentiated functions and lose others. These developmental changes involve extensive alterations...

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Section: Discussionsupporting

confidence: 90%

Selective translational control and nonspecific posttranscriptional regulation of ribosomal protein gene expression during development and regeneration of rat liver.

Aloni¹,

Peleg²,

Meyuhas³

1992

Mol. Cell. Biol.

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“…Alternatively, the expression we detected in the fetal liver may be due to cells other than hepatocytes. For example the fetal liver is active in hemopoesis and there is a rapid drop in hemopoeitic cells around the time of birth [16] which would fit with the decline in Mnk mRNA from the fetal to neonatal period. We have attempted to identify the cellular location of the Mnk mRNA using in situ hybridization to liver sections, but to date the mRNA has not been detected with this technique.…”

Section: Resultsmentioning

confidence: 99%

Expression of the Menkes gene homologue in mouse tissues lack of effect of copper on the mRNA levels

et al. 1994

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The expression of the homologue of the Menkes disease gene (Mnk) in mice was studied using RNA blots. The highest level of expression of the 8.0 kb mRNA was found in placenta, substantial expression was noted in lung, heart, brain, testis and kidney and gut mucosa, but very low levels were found in spleen and adult liver. In fetal liver, the amount of Mnk mRNA is similar to that found in kidney, however, it declines soon after birth. Results with copper-loaded normal mice and mutant mice with genetic defects in copper transport suggested that Mnk mRNA levels are not regulated by tissue copper concentrations.

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“…However, the changing cytology of the maturing liver makes necessary further comment on the quantitative significance of the results. Oliver, Blumer & Witham (1963) examined the cellular composition of the maturing rat liver and found that, in the 17-day foetal rat, about 60% of the tissue consisted of haemopoietic cells and vascular space. By the sixth post-natal day, the value assigned to non-parenchymal tissue had fallen in an almost linear fashion to the adult level of 10% vascular space, and haemopoietic tissue was absent.…”

Section: Resultsmentioning

confidence: 99%

Plasma albumin synthesis during neonatal development of the rat

Wise

Oliver

1967

Biochemical Journal

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1. Liver slices were incubated with (14)C-labelled amino acids. Albumin was isolated from the slices by precipitation with specific antibody and the incorporated radioactivity measured. 2. The rate of synthesis was seen to be equal in liver slices from adult and late-stage foetal rats. 3. Synthesis was very high in the pregnant rat (three times the normal adult value) and in the 5-15-day post-natal rat (twice the normal adult value). 4. The post-natal increase may be due to the disappearance of haemopoietic tissue and its replacement by active parenchymal cells.

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Free ribosomes during maturation of rat liver

Cited by 59 publications

References 8 publications

Selective translational control and nonspecific posttranscriptional regulation of ribosomal protein gene expression during development and regeneration of rat liver.

Selective translational control and nonspecific posttranscriptional regulation of ribosomal protein gene expression during development and regeneration of rat liver.

Expression of the Menkes gene homologue in mouse tissues lack of effect of copper on the mRNA levels

Plasma albumin synthesis during neonatal development of the rat

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