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

Abstract

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...

Purification and Characterization of a 5′ to 3′ Exoribonuclease from Rabbit Reticulocytes that Degrades Capped and Uncapped RNAs

“…Previous work in this laboratory has shown that EF-la mRNA is rapidly degraded in vivo in MEL cells under certain growth conditions [28] and is also rapidly degraded in vitro [27]. However, attempts to establish an in vitro decay system [29] using messenger ribonucleoprotein particles and postribosomal 130 OOOXg supernatant proteins was unsuccessful.…”

Molecular characterization and expression analysis of nine cotton GhEF1A genes encoding translation elongation factor 1A

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A translation elongation factor 1A (CaEF1A) gene from hot pepper (Capsicum annuum L.) is induced by the tobacco mosaic virus and by wounding

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