scholarly journals Cyclin-Dependent Kinase 12 Increases 3′ End Processing of Growth Factor-Induced c-FOS Transcripts

2014 ◽  
Vol 35 (2) ◽  
pp. 468-478 ◽  
Author(s):  
Tristan T. Eifler ◽  
Wei Shao ◽  
Koen Bartholomeeusen ◽  
Koh Fujinaga ◽  
Stefanie Jäger ◽  
...  
Keyword(s):  
Growth Factor ◽  
Rna Polymerase ◽  
Rna Polymerase Ii ◽  
Mammalian Cells ◽  
Dominant Negative ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Eukaryotic Translation ◽  
Eukaryotic Translation Initiation ◽  
Specificity Factor

Transcriptional cyclin-dependent kinases (CDKs) regulate RNA polymerase II initiation and elongation as well as cotranscriptional mRNA processing. In this report, we describe an important role for CDK12 in the epidermal growth factor (EGF)-induced c-FOS proto-oncogene expression in mammalian cells. This kinase was found in the exon junction complexes (EJC) together with SR proteins and was thus recruited to RNA polymerase II. In cells depleted of CDK12 or eukaryotic translation initiation factor 4A3 (eIF4A3) from the EJC, EGF induced fewer c-FOS transcripts. In these cells, phosphorylation of serines at position 2 in the C-terminal domain (CTD) of RNA polymerase II, as well as levels of cleavage-stimulating factor 64 (Cstf64) and 73-kDa subunit of cleavage and polyadenylation specificity factor (CPSF73), was reduced at the c-FOS gene. These effects impaired 3′ end processing of c-FOS transcripts. Mutant CDK12 proteins lacking their Arg-Ser-rich (RS) domain or just the RS domain alone acted as dominant negative proteins. Thus, CDK12 plays an important role in cotranscriptional processing of c-FOS transcripts.

scholarly journals Efficient Translation of Rotavirus mRNA Requires Simultaneous Interaction of NSP3 with the Eukaryotic Translation Initiation Factor eIF4G and the mRNA 3′ End

2000 ◽  
Vol 74 (15) ◽  
pp. 7064-7071 ◽  
Author(s):  
Patrice Vende ◽  
Maria Piron ◽  
Nathalie Castagné ◽  
Didier Poncet
Keyword(s):  
Translation Initiation ◽  
Mammalian Cells ◽  
Consensus Sequence ◽  
Mrna Translation ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Viral Mrna ◽  
Eukaryotic Translation Initiation Factor ◽  
Eukaryotic Translation ◽  
Eukaryotic Translation Initiation

ABSTRACT In contrast to the vast majority of cellular proteins, rotavirus proteins are translated from capped but nonpolyadenylated mRNAs. The viral nonstructural protein NSP3 specifically binds the 3′-end consensus sequence of viral mRNAs and interacts with the eukaryotic translation initiation factor eIF4G. Here we show that expression of NSP3 in mammalian cells allows the efficient translation of virus-like mRNA. A synergistic effect between the cap structure and the 3′ end of rotavirus mRNA was observed in NSP3-expressing cells. The enhancement of viral mRNA translation by NSP3 was also observed in a rabbit reticulocyte lysate translation system supplemented with recombinant NSP3. The use of NSP3 mutants indicates that its RNA- and eIF4G-binding domains are both required to enhance the translation of viral mRNA. The results reported here show that NSP3 forms a link between viral mRNA and the cellular translation machinery and hence is a functional analogue of cellular poly(A)-binding protein.

scholarly journals Translational control of programmed cell death: eukaryotic translation initiation factor 4E blocks apoptosis in growth-factor-restricted fibroblasts with physiologically expressed or deregulated Myc.

1996 ◽  
Vol 16 (11) ◽  
pp. 6573-6581 ◽  
Author(s):  
V A Polunovsky ◽  
I B Rosenwald ◽  
A T Tan ◽  
J White ◽  
L Chiang ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Growth Factor ◽  
Translation Initiation ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Individual Growth ◽  
Eukaryotic Translation Initiation Factor ◽  
Eukaryotic Translation ◽  
Eukaryotic Translation Initiation ◽  
Survival Signaling

There is increasing evidence that cell cycle transit is potentially lethal, with survival depending on the activation of metabolic pathways which block apoptosis. However, the identities of those pathways coupling cell cycle transit to survival remain undefined. Here we show that the eukaryotic translation initiation factor 4E (eIF4E) can mediate both proliferative and survival signaling. Overexpression of eIF4E completely substituted for serum or individual growth factors in preserving the viability of established NIH 3T3 fibroblasts. An eIF4E mutant (Ser-53 changed to Ala) defective in mediating its growth-factor-regulated functions was also defective in its survival signaling. Survival signaling by enforced expression of eIF4E did not result from autocrine release of survival factors, nor did it lead to increased expression of the apoptosis antagonists Bcl-2 and Bcl-XL. In addition, the execution apparatus of the apoptotic response in eIF4E-overexpressing cells was found to be intact. Increased expression of eIF4E was sufficient to inhibit apoptosis in serum-restricted primary fibroblasts with enforced expression of Myc. In contrast, activation of Ha-Ras, which is required for eIF4E proliferative signaling, did not suppress Myc-induced apoptosis. These data suggest that the eIF4E-activated pathways leading to survival and cell cycle progression are distinct. This dual signaling of proliferation and survival might be the basis for the potency of eIF4E as an inducer of neoplastic transformation.

scholarly journals Cleavage of Poly(A)-Binding Protein by Poliovirus 3C Protease Inhibits Host Cell Translation: a Novel Mechanism for Host Translation Shutoff

2004 ◽  
Vol 24 (4) ◽  
pp. 1779-1790 ◽  
Author(s):  
N. Muge Kuyumcu-Martinez ◽  
Marc E. Van Eden ◽  
Patrick Younan ◽  
Richard E. Lloyd
Keyword(s):  
Mammalian Cells ◽  
Binding Protein ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Translation Inhibition ◽  
Eukaryotic Translation ◽  
3C Protease ◽  
Dual Strategy ◽  
Eukaryotic Translation Initiation ◽  
Infected Cells

ABSTRACT Cleavage of eukaryotic translation initiation factor 4GI (eIF4GI) by viral 2A protease (2Apro) has been proposed to cause severe translation inhibition in poliovirus-infected cells. However, infections containing 1 mM guanidine-HCl result in eIF4GI cleavage but only partial translation shutoff, indicating eIF4GI cleavage is insufficient for drastic translation inhibition. Viral 3C protease (3Cpro) cleaves poly(A)-binding protein (PABP) and removes the C-terminal domain (CTD) that interacts with several translation factors. In HeLa cell translation extracts that exhibit cap-poly(A) synergy, partial cleavage of PABP by 3Cpro inhibited translation of endogenous mRNAs and reporter RNA as effectively as complete cleavage of eIF4GI and eIF4GII by 2Apro. 3Cpro-mediated translation inhibition was poly(A) dependent, and addition of PABP to extracts restored translation. Expression of 3Cpro in HeLa cells resulted in partial PABP cleavage and similar inhibition of translation. PABP cleavage did not affect eIF4GI-PABP interactions, and the results of kinetics experiments suggest that 3Cpro might inhibit late steps in translation or ribosome recycling. The data illustrate the importance of the CTD of PABP in poly(A)-dependent translation in mammalian cells. We propose that enteroviruses use a dual strategy for host translation shutoff, requiring cleavage of PABP by 3Cpro and of eIF4G by 2Apro.

scholarly journals Interaction of Eukaryotic Translation Initiation Factor 4G with the Nuclear Cap-Binding Complex Provides a Link between Nuclear and Cytoplasmic Functions of the m7Guanosine Cap

2001 ◽  
Vol 21 (11) ◽  
pp. 3632-3641 ◽  
Author(s):  
Linda McKendrick ◽  
Elizabeth Thompson ◽  
Joao Ferreira ◽  
Simon J. Morley ◽  
Joe D. Lewis
Keyword(s):  
Translation Initiation ◽  
Mammalian Cells ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Eukaryotic Translation Initiation Factor ◽  
Eukaryotic Translation ◽  
Eukaryotic Translation Initiation ◽  
Cap Binding Complex

ABSTRACT In eukaryotes the majority of mRNAs have an m7G cap that is added cotranscriptionally and that plays an important role in many aspects of mRNA metabolism. The nuclear cap-binding complex (CBC; consisting of CBP20 and CBP80) mediates the stimulatory functions of the cap in pre-mRNA splicing, 3′ end formation, and U snRNA export. As little is known about how nuclear CBC mediates the effects of the cap in higher eukaryotes, we have characterized proteins that interact with CBC in HeLa cell nuclear extracts as potential mediators of its function. Using cross-linking and coimmunoprecipitation, we show that eukaryotic translation initiation factor 4G (eIF4G), in addition to its function in the cytoplasm, is a nuclear CBC-interacting protein. We demonstrate that eIF4G interacts with CBC in vitro and that, in addition to its cytoplasmic localization, there is a significant nuclear pool of eIF4G in mammalian cells in vivo. Immunoprecipitation experiments suggest that, in contrast to the cytoplasmic pool, much of the nuclear eIF4G is not associated with eIF4E (translation cap binding protein of eIF4F) but is associated with CBC. While eIF4G stably associates with spliceosomes in vitro and shows close association with spliceosomal snRNPs and splicing factors in vivo, depletion studies show that it does not participate directly in the splicing reaction. Taken together the data indicate that nuclear eIF4G may be recruited to pre-mRNAs via its interaction with CBC and accompanies the mRNA to the cytoplasm, facilitating the switching of CBC for eIF4F. This may provide a mechanism to couple nuclear and cytoplasmic functions of the mRNA cap structure.

scholarly journals Phosphorylation of the Cap-Binding Protein Eukaryotic Translation Initiation Factor 4E by Protein Kinase Mnk1 In Vivo

1999 ◽  
Vol 19 (3) ◽  
pp. 1871-1880 ◽  
Author(s):  
Andrew Jan Waskiewicz ◽  
Jeffrey C. Johnson ◽  
Bennett Penn ◽  
Malathy Mahalingam ◽  
Scot R. Kimball ◽  
...  
Keyword(s):  
Translation Initiation ◽  
Dominant Negative ◽  
Translation Initiation Factor ◽  
Scaffolding Protein ◽  
Initiation Factor ◽  
Eukaryotic Translation Initiation Factor ◽  
Eukaryotic Translation ◽  
Eukaryotic Translation Initiation ◽  
In Cells

ABSTRACT Eukaryotic translation initiation factor 4E (eIF4E) binds to the mRNA 5′ cap and brings the mRNA into a complex with other protein synthesis initiation factors and ribosomes. The activity of mammalian eIF4E is important for the translation of capped mRNAs and is thought to be regulated by two mechanisms. First, eIF4E is sequestered by binding proteins, such as 4EBP1, in quiescent cells. Mitogens induce the release of eIF4E by stimulating the phosphorylation of 4EBP1. Second, mitogens and stresses induce the phosphorylation of eIF4E at Ser 209, increasing the affinity of eIF4E for capped mRNA and for an associated scaffolding protein, eIF4G. We previously showed that a mitogen- and stress-activated kinase, Mnk1, phosphorylates eIF4E in vitro at the physiological site. Here we show that Mnk1 regulates eIF4E phosphorylation in vivo. Mnk1 binds directly to eIF4G and copurifies with eIF4G and eIF4E. We identified activating phosphorylation sites in Mnk1 and developed dominant-negative and activated mutants. Expression of dominant-negative Mnk1 reduces mitogen-induced eIF4E phosphorylation, while expression of activated Mnk1 increases basal eIF4E phosphorylation. Activated mutant Mnk1 also induces extensive phosphorylation of eIF4E in cells overexpressing 4EBP1. This suggests that phosphorylation of eIF4E is catalyzed by Mnk1 or a very similar kinase in cells and is independent of other mitogenic signals that release eIF4E from 4EBP1.

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