CK2 phosphorylation of eukaryotic translation initiation factor 5 potentiates cell cycle progression

Homma, Miwako K.; Wada, Ikuo; Suzuki, Toshiyuki; Yamaki, Junko; Krebs, Edwin G.; Homma, Yoshimi

doi:10.1073/pnas.0506791102

Cited by 59 publications

(52 citation statements)

References 28 publications

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“…Site-directed mutagenesis of eIF5 to remove CK2 phosphorylation sites not only prevented the CK2-mediated increase in its interaction with eIF1 and eIF3c but also resulted in reduced stimulation of translation initiation by eIF5 in vitro. This supports findings with mammalian cells, where the expression of mutants that prevented CK2 phosphorylation disrupted synchronous cell cycle progression and significantly reduced growth rates (19).…”

Section: Discussionsupporting

confidence: 77%

“…The interaction of the eIF5 C terminus with the N-terminal domain of eIF2␤ has been previously demonstrated in yeast (12). Studies in mammalian cells suggest that the eIF2/eIF5 interaction may be dependent on CK2 phosphorylation of eIF5 (19).…”

Section: Effect Of Ck2 Phosphorylation On His-eif5 Pulldownsmentioning

confidence: 99%

“…Phosphorylation of the eIF5 C-terminal HEAT domain appears to be conserved in mammals (17), yeast (18), and plants (this study). Expression of mutant mammalian eIF5 with alanine substitutions at CK2 phosphorylation sites reduced the formation of eIF5-eIF2 complexes in vivo, and resulted in significant reductions in growth suggesting regulation by CK2 phosphorylation (19).…”

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confidence: 99%

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Phosphorylation of Plant Translation Initiation Factors by CK2 Enhances the in Vitro Interaction of Multifactor Complex Components

Dennis

Person

Browning

2009

Journal of Biological Chemistry

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CK2 phosphorylates a wide variety of substrates, including translation initiation factors. A mass spectrometric approach was used to identify residues phosphorylated by CK2, which may regulate the activity of initiation factors during the translation initiation process in plants. CK2 in vitro phosphorylation sites were identified in wheat and Arabidopsis thaliana eIF2␣, eIF2␤, eIF5, and wheat eIF3c. Native wheat eIF5 and eIF2␣ were found to have phosphorylation sites that corresponded to some of the in vitro CK2 phosphorylation sites. A large number of the CK2 sites identified in this study are in conserved binding domains that have been implicated in the yeast multifactor complex (eIF1-eIF3-eIF5-eIF2-GTP-Met-tRNA i Met ). This is the first study to demonstrate that plant initiation factors are capable of forming a multifactor complex in vitro. In addition, the interaction of factors within these complexes was enhanced both in vitro and in native extracts by phosphorylation of one or more initiation factors by CK2. The importance of CK2 phosphorylation of eIF5 was evaluated by site-directed mutagenesis of eIF5 to remove CK2 phosphorylation sites. Removal of CK2 phosphorylation sites from eIF5 inhibits the CK2-mediated increase in eIF5 interaction with eIF1 and eIF3c in pulldown assays and reduces the eIF5-mediated stimulation of translation initiation in vitro. These results suggest a functional role for CK2 phosphorylation in the initiation of plant translation.Translation initiation is a critical, rate-limiting step in eukaryotic gene expression, with a key step early in the pathway being the assembly of the 43 S preinitiation complex (1, 2). This 43 S preinitiation complex is composed of the small 40 S ribosomal subunit, eIF1, eIF1A, the eIF2-GTP-Met-tRNA i Met ternary complex, eIF3, and eIF5. Biochemical data from yeast suggest that a multifactor complex (MFC) 2 consisting of eIF3-eIF1-eIF5-eIF2-GTP-Met-tRNA i Met exists free of the ribosome allowing these factors to be simultaneously loaded onto the 40 S ribosomal subunit (3). Mutations that disrupt the interaction of factors within this complex result in substantial reductions in translation initiation (3, 4). Using a variety of in vitro binding assays, two-hybrid analysis, and in vivo purification of affinity-tagged subunits, an extensive analysis of the subunit interactions within the yeast MFC has resulted in a provisional model of the yeast MFC (5). The yeast eIF3c (NIP1) N-terminal domain plays a particularly important role in binding to other initiation factors in the context of the multifactor complex (6). The NIP1 N-terminal domain was found to bind directly to both eIF1 and eIF5 (7,8), and it is suspected that this binding coordinates the interaction between eIF1 and eIF5 that is responsible for the inhibition of GTP hydrolysis at non-AUG codons (6). The C-terminal domain (CTD) of yeast eIF5 simultaneously binds to both the N terminus of eIF3c, the N-terminal K-boxes of eIF2␤, and eIF1 (3, 9). This creates an indirect link between eIF3c and eIF2␤,...

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Section: Discussionsupporting

confidence: 77%

Section: Effect Of Ck2 Phosphorylation On His-eif5 Pulldownsmentioning

confidence: 99%

mentioning

confidence: 99%

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Phosphorylation of Plant Translation Initiation Factors by CK2 Enhances the in Vitro Interaction of Multifactor Complex Components

Dennis

Person

Browning

2009

Journal of Biological Chemistry

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“…CK2 has been widely characterized as an important regulator of the cell cycle and has been found to regulate cell-cycle transition through multiple phases in a (30)(31)(32)(33)(34)(35). Activated Akt has been reported to phosphorylate and thereby decrease the proteosomal stability of the p21 and p27 cell-cycle inhibitor proteins allowing cell-cycle progression (36,37).…”

Section: Cell-cycle Arrest and Caspase 3/7 Activationmentioning

confidence: 99%

CX-4945, an Orally Bioavailable Selective Inhibitor of Protein Kinase CK2, Inhibits Prosurvival and Angiogenic Signaling and Exhibits Antitumor Efficacy

Siddiqui‐Jain¹,

Drygin²,

Streiner³

et al. 2010

Cancer Research

465

421

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Malignant transformation and maintenance of the malignant phenotype depends on oncogenic and nononcogenic proteins that are essential to mediate oncogene signaling and to support the altered physiologic demands induced by transformation. Protein kinase CK2 supports key prosurvival signaling pathways and represents a prototypical non-oncogene. In this study, we describe CX-4945, a potent and selective orally bioavailable small molecule inhibitor of CK2. The antiproliferative activity of CX-4945 against cancer cells correlated with expression levels of the CK2a catalytic subunit. Attenuation of PI3K/Akt signaling by CX-4945 was evidenced by dephosphorylation of Akt on the CK2-specific S129 site and the canonical S473 and T308 regulatory sites. CX-4945 caused cell-cycle arrest and selectively induced apoptosis in cancer cells relative to normal cells. In models of angiogenesis, CX-4945 inhibited human umbilical vein endothelial cell migration, tube formation, and blocked CK2-dependent hypoxia-induced factor 1 alpha (HIF-1a) transcription in cancer cells. When administered orally in murine xenograft models, CX-4945 was well tolerated and demonstrated robust antitumor activity with concomitant reductions of the mechanism-based biomarker phospho-p21 (T145). The observed antiproliferative and anti-angiogenic responses to CX-4945 in tumor cells and endothelial cells collectively illustrate that this compound exerts its antitumor effects through inhibition of CK2-dependent signaling in multiple pathways. Finally, CX-4945 is the first orally bioavailable small molecule inhibitor of CK2 to advance into human clinical trials, thereby paving the way for an entirely new class of targeted treatment for cancer. Cancer Res; 70(24); 10288-98. Ó2010 AACR.

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“…may be regulated by eIF4G, which is phosphorylated at a number of different sites, but how the function of the protein is affected has not been elucidated. eIF5 is phosphorylated by casein kinase 2, which promotes initiation and affects cell-cycle progression (26). eIF5B and PABP can be phosphorylated, but possible functional effects are not known.…”

Section: Other Initiation Reactionsmentioning

confidence: 99%

Regulation of protein synthesis and the role of eIF3 in cancer

Hershey¹

2010

Braz J Med Biol Res

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CK2 phosphorylation of eukaryotic translation initiation factor 5 potentiates cell cycle progression

Cited by 59 publications

References 28 publications

Phosphorylation of Plant Translation Initiation Factors by CK2 Enhances the in Vitro Interaction of Multifactor Complex Components

Phosphorylation of Plant Translation Initiation Factors by CK2 Enhances the in Vitro Interaction of Multifactor Complex Components

CX-4945, an Orally Bioavailable Selective Inhibitor of Protein Kinase CK2, Inhibits Prosurvival and Angiogenic Signaling and Exhibits Antitumor Efficacy

Regulation of protein synthesis and the role of eIF3 in cancer

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