Regulation of the utilization of mRNA for eucaryotic elongation factor Tu in Friend erythroleukemia cells.

Rao, Tekmal R.; Slobin, Lawrence I.

doi:10.1128/mcb.7.2.687

Cited by 31 publications

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“…2; Table 2) and poly(A)+ (Table 2; Rapid destabilization of eEF-Tu on treatment of stationary FEL cells with fresh medium. As mentioned above, we previously reported a large and rapid loss of eEF-Tu mRNA when stationary FEL cells were treated with fresh medium (35). These results imply that the stability of eEF-Tu mRNA is markedly altered when FEL cells resume growth.…”

Section: Methodssupporting

confidence: 60%

“…After 1 h in fresh medium, approximately 90% of eEF-Tu mRNA in FEL cells was found in heavy polysomes. Associated with the shift of eEF-Tu mRNA into heavy polysomes, a remarkable 40% decrease in the total amount of eEF-Tu mRNA per cell was observed (35). Our data raised the possibility that the eEFTu mRNA that accumulated in mRNP particles in stationary-phase cells was degraded rather than reutilized for protein synthesis.…”

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“…FEL cells were grown at 37°C in Ham F-10 containing 5% bovine calf serum as described previously (35). The cell number was determined with a hemacytometer.…”

Section: Methodsmentioning

confidence: 99%

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The stability of mRNA for eucaryotic elongation factor Tu in Friend erythroleukemia cells varies with growth rate.

Rao¹,

Slobin²

1988

Mol. Cell. Biol.

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The decay rates of eucaryotic elongation factor Tu (eEF-Tu) mRNA and eucaryotic initiation factor 4A (eIF-4A) mRNA in Friend erythroleukemia (FEL) cells were determined under several different growth conditions. In FEL cells which were no longer actively dividing (stationary phase), eEF-Tu mRNA was found to be rather stable, with a tl2 of about 24 h. In rapidly growing FEL cells eEF-Tu mRNA was considerably less stable, with a t4/2 of about 9 h. In both cases a single rate of mRNA decay was observed. However, when stationary-phase cells resumed growth after treatment with fresh medium, we observed that eEF-Tu mRNA decay followed a biphasic process. The faster of the two decay rates involved approximately 50% of the eEF-Tu mRNA and had a tl2 of about 1 h. The decay rates for eIF-4A (tl/2 = 2 h) and total poly(A)+ RNA (tl2 = 3 h) were unaffected by changes in growth conditions. The 4,2 for polysomal eEF-Tu mRNA was found to be about 8 h when stationary FEL cells were treated with fresh medium. Previous work in this laboratory has shown (T. R. Rao and L. I. Slobin, Mol. Cell. Biol. 7:687-697, 1987) that when FEL cells are allowed to grow to stationary phase, approximately 60% of the mRNA for eEF-Tu is found in a nontranslating postpolysomal messenger ribonucleoprotein (mRNP) particle. eEF-Tu mRNP was rapidly cleared from stationary cells after treatment with fresh medium. The data presented in this report indicate that the stability of eEF-Tu mRNP is rapidly altered and the particle is targeted for degradation when stationary FEL cells resume growth.Of the processes which regulate the expression of genes, the ones which determine the stability of mRNA in the cytoplasm of cells are among the least well understood. In general, individual eucaryotic mRNAs have characteristic rates of decay within a given cell type, with different mRNAs having widely different stabilities. It has also become apparent that many mRNAs have variable rates of decay under different physiological conditions (37). For example, the stability of histone mRNAs changes during the cell cycle (19), and the stability of numerous mRNAs is influenced by treatment of sensitive cells with the appropriate hormones (4,5,17). Recent studies have implicated both the 5' leader region and the 3' untranslated sequence of certain mRNAs as targets for the initiation of the mRNA decay process (3,16,26,38). However, other factors besides sequence must be important in regulating mRNA stability if the half-life of a given mRNA is variable within a given cell type.The necessity of accounting for variability in mRNA half-life has led several investigators to consider the possible role of the translational process in the regulation of mRNA stability. Two types of regulation have been suggested on the basis of the use of different inhibitors of protein synthesis. For example, both cycloheximide (an elongation inhibitor) and pactamycin (an initiation inhibitor) were found to stabilize histone mRNA when DNA replication was blocked (39) and to stabilize c-myc mRNA (26). Th...

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confidence: 60%

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The stability of mRNA for eucaryotic elongation factor Tu in Friend erythroleukemia cells varies with growth rate.

Rao¹,

Slobin²

1988

Mol. Cell. Biol.

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“…Studies of the elongation factor eEF-la show that its synthesis is strongly reduced in Friend erythroleukemia cells at stationary phase and is stimulated when cells are treated with fresh serum-containing medium. Regulation involves changes in mRNA translation efficiency (polysome size) and mRNA levels, the latter by affecting mRNA stability (34,35).In earlier reports, we evaluated the levels and synthesis rates of a number of initiation factors in HeLa cells deprived of or stimulated by serum (9, 10). Of those factors examined, most (eIF-2, eIF-3, eIF-4B, and eIF-4Fp220) were approximately equimolar with ribosomes in these cells, whereas two (eIF-4A and eIF-4D) were three-to fourfold higher in concentration and at least one (eIF-4E) was about threefold lower.…”

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Translational initiation factor expression and ribosomal protein gene expression are repressed coordinately but by different mechanisms in murine lymphosarcoma cells treated with glucocorticoids.

Huang¹

1989

Mol. Cell. Biol.

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P1798 murine lymphosarcoma cells cease to proliferate upon exposure to 10-7 M dexamethasone and exhibit a dramatic inhibition of rRNA and ribosomal protein synthesis (0. Meyuhas, E. Thompson, Jr., and R. P. Perry, Mol. Cell Biol. 7:2691-2699. These workers demonstrated that ribosomal protein synthesis is regulated primarily at the level of translation, since dexamethasone did not alter mRNA levels but shifted the mRNAs from active polysomes into inactive messenger ribonucleoproteins. We have examined the effects of dexamethasone on the biosynthesis of initiation factor proteins in the same cell line. The relative protein synthesis rates of eIF-4A and eIF-2a were inhibited by about 70% by the hormone, a reduction comparable to that for ribosomal proteins. The mRNA levels of eIF-4A, eIF-4D, and eIF-2a also were reduced by 60 to 70%, indicating that synthesis rates are proportional to mRNA concentrations. Analysis of polysome profiles showed that the average number of ribosomes per initiation factor polysome was only slightly reduced by dexamethasone, and little or no mRNA was present in messenger ribonucleoproteins. The results indicate that initiation factor gene expression is coordinately regulated with ribosomal protein synthesis but is controlled primarily by modulating mRNA levels rather than mRNA efficiency.Biosynthesis of the translational apparatus, namely, ribosomes and their associated soluble factors, involves the coordinate accumulation of a large number of proteins. The expression of ribosomal protein genes in bacteria is coordinated in large part at the level of translation, where autogenous regulation of the translation of operon mRNA occurs by feedback inhibition with one of the ribosomal protein products (30). In mammalian cells, ribosomal protein synthesis appears not to be regulated autogenously (6,18,20,40); instead, protein turnover plays a key role in their balanced accumulation (1,18,21). Much less is known about the regulation of gene expression for the mammalian soluble factors. Studies of the elongation factor eEF-la show that its synthesis is strongly reduced in Friend erythroleukemia cells at stationary phase and is stimulated when cells are treated with fresh serum-containing medium. Regulation involves changes in mRNA translation efficiency (polysome size) and mRNA levels, the latter by affecting mRNA stability (34,35).In earlier reports, we evaluated the levels and synthesis rates of a number of initiation factors in HeLa cells deprived of or stimulated by serum (9, 10). Of those factors examined, most (eIF-2, eIF-3, eIF-4B, and eIF-4Fp220) were approximately equimolar with ribosomes in these cells, whereas two (eIF-4A and eIF-4D) were three-to fourfold higher in concentration and at least one (eIF-4E) was about threefold lower. The relative synthesis and turnover rates of both ribosomal proteins and initiation factors are not altered in these cells by growth rate changes caused by serum; the translational components follow total protein synthesis and degradation rates (10). We are i...

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TOP Genes: A Translationally Controlled Class of Genes Including Those Coding for Ribosomal Proteins

Amaldi

Pierandrei-Amaldi

1997

Progress in Molecular and Subcellular Biology

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Regulation of the utilization of mRNA for eucaryotic elongation factor Tu in Friend erythroleukemia cells.

Cited by 31 publications

References 44 publications

The stability of mRNA for eucaryotic elongation factor Tu in Friend erythroleukemia cells varies with growth rate.

The stability of mRNA for eucaryotic elongation factor Tu in Friend erythroleukemia cells varies with growth rate.

Translational initiation factor expression and ribosomal protein gene expression are repressed coordinately but by different mechanisms in murine lymphosarcoma cells treated with glucocorticoids.

TOP Genes: A Translationally Controlled Class of Genes Including Those Coding for Ribosomal Proteins

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