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Biomedical subjects

R G Vries

Publications and source records attributed to R G Vries.

4 recordsLinked to original sources
PubMed1998

The phosphorylation of eukaryotic initiation factor eIF4E in response to phorbol esters, cell stresses, and cytokines is mediated by distinct MAP kinase pathways.

Initiation factor eIF4E binds to the 5'-cap of eukaryotic mRNAs and plays a key role in the mechanism and regulation of translation. It may be regulated through its own phosphorylation and through inhibitory binding proteins (4E-BPs), which modulate its availability for initiation complex assembly. eIF4E phosphorylation is enhanced by phorbol esters. We show, using specific inhibitors, that this involves both the p38 mitogen-activated protein (MAP) kinase and Erk signaling pathways. Cell stresses such as arsenite and anisomycin and the cytokines tumor necrosis factor-alpha and interleukin-1beta also cause increased phosphorylation of eIF4E, which is abolished by the specific p38 MAP kinase inhibitor, SB203580. These changes in eIF4E phosphorylation parallel the activity of the eIF4E kinase, Mnk1. However other stresses such as heat shock, sorbitol, and H2O2, which also stimulate p38 MAP kinase and increase Mnk1 activity, do not increase phosphorylation of eIF4E. The latter stresses increase the binding of eIF4E to 4E-BP1, and we show that this blocks the phosphorylation of eIF4E by Mnk1 in vitro, which may explain the absence of an increase in eIF4E phosphorylation under these conditions.

Animals↗
PubMed1997

Heat shock increases the association of binding protein-1 with initiation factor 4E.

The effects of heat shock on the regulation of the cap-binding initiation factor 4E (eIF4E) and its inhibitory binding protein, 4E-BP1, have been examined in Chinese hamster ovary cells and in cardiac myocytes. Heat shock increased the association between eIF4E and 4E-BP1, and this was associated with a dephosphorylation of 4E-BP1. These effects did not appear to be due wholly to decreased activity of the p70 S6 kinase pathway, which is implicated in the control of 4E-BP1, and they were not mediated by the stress-activated p38 microtubule-associated protein kinase pathway. Increased binding of 4E-BP1 to eIF4E correlated with a decrease in the amount of eIF4G which co-purified with the latter. This could account for the previously observed impairment of eIF4F function during heat shock, and, since heat shock protein mRNAs are believed to be relatively cap-independent, could provide a mechanism for the selective up-regulation of the synthesis of heat shock proteins and other stress proteins during heat shock.

Animals↗
PubMed1997

Translational properties of the untranslated regions of the p10 messenger RNA of Autographa californica multicapsid nucleopolyhedrovirus.

Protein yields in the baculovirus expression system do not always correlate with the presence of abundant amounts of corresponding mRNAs. Therefore, a novel aspect of the baculovirus expression system was studied: initiation of translation of very late mRNAs of Autographa californica multicapsid nucleopolyhedrovirus. The untranslated regions (UTRs) of the p10 mRNA of this baculovirus were studied by in vitro translation and after transfection into Spodoptera frugiperda insect cells. Lysates from insect cells were optimized for translation of in vitro transcripts containing p10 sequences. The lysates were used to measure the effects of various deletions in either the 5' or 3'UTR on protein synthesis. Transcripts containing the p10 5'UTR were translated efficiently. Large deletions in the 5'UTR severely decreased this efficiency. Deletions in the 3'UTR negatively affected expression of the reporter gene in vivo; however, no effect on translational efficiency in the insect-cell lysates was measured. The translational properties of the p10 transcripts were very similar in lysates made from either uninfected or baculovirus-infected insect cells. Determination of optimal salt conditions for either uncapped or capped transcripts showed that the p10 5'UTR was used very efficiently for translation initiation in vitro, even in the absence of a cap-structure at its 5' end. Addition of cap-analogue to the in vitro translation assays did not inhibit p10 5'UTR-driven translation, while translation of a cap-dependent mRNA was severely inhibited. These data suggest that the very late mRNAs of baculovirus are translated in a cap-independent manner.

Animals↗