scholarly journals WD Repeat Domain 77 Protein Regulates Translation of E2F1 and E2F3 mRNA

2020 ◽  
Vol 40 (24) ◽  
Author(s):  
Mahmood Anber Altayyar ◽  
Xiumei Sheng ◽  
Zhengxin Wang
Keyword(s):  
Cell Growth ◽  
Translational Regulation ◽  
Cellular Proliferation ◽  
Inhibitory Effect ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Lung Tumorigenesis ◽  
Prostate Tumorigenesis ◽  
Repeat Domain ◽  
Wd Repeat

ABSTRACT WD repeat domain 77 protein (WDR77) is required for cellular proliferation of lung and prostate epithelial cells during earlier stages of development and is reactivated during prostate and lung tumorigenesis. WDR77 plays an essential role in prostate tumorigenesis and cell growth mediated by growth regulatory factors. Here, we identified E2F1 and E2F3 mRNAs as translational targets of WDR77. We demonstrated that WDR77 regulated the translation of E2F1 and E2F3 mRNAs through the 5′ untranslated regions (UTRs) of E2F1 and E2F3 (E2F1/3) mRNAs. WDR77 physically interacted with programmed cell death 4 (PDCD4) that suppresses translation of mRNAs containing structured 5′ UTRs by interacting with eukaryotic translation initiation factor 4A (eIF4A) and inhibiting its helicase activity. Further, we demonstrated that the interaction between WDR77 and PDCD4 prevented the binding of PDCD4 to eIF4A and relieved PDCD4's inhibitory effect on eIF4A1. Overall, our work reveals for the first time that WDR77 is directly involved in translational regulation of E2F1/3 mRNAs through their structured 5′ UTRs, PDCD4, and eIF4A1 and provides novel insight into the cell growth controlled by WDR77.

scholarly journals Effects of chronic 5′-{[(Z)-4-amino-2-butenyl]methylamino)-5′-deoxy- adenosine (AbeAdo) treatment on polyamine and eIF-5A metabolism in AbeAdo-sensitive and -resistant L1210 murine leukaemia cells

1993 ◽  
Vol 290 (1) ◽  
pp. 115-121 ◽  
Author(s):  
T L Byers ◽  
L Wiest ◽  
R S Wechter ◽  
A E Pegg
Keyword(s):  
Cell Growth ◽  
Translation Initiation ◽  
Chronic Exposure ◽  
Limit Of Detection ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Eukaryotic Translation ◽  
L1210 Cells ◽  
Eukaryotic Translation Initiation ◽  
Exogenous Spermidine

We have previously reported that prolonged chronic exposure to the S-adenosyl-L-methionine decarboxylase (AdoMetDC) inhibitor, 5′-([(Z)-4-amino-2-butenyl]methylamino)-5′-deoxy-adenosine (MDL 73811, AbeAdo), leads to cytostasis of L1210 cells [Byers, Ganem and Pegg (1992) Biochem. J. 287, 717-724]. Further studies to investigate the mechanism by which these effects are brought about were carried out by comparing an L1210-derived cell line (R20) that is resistant to AbeAdo with the parent cells. The R20 cells were derived by two rounds of AbeAdo-induced cytostasis followed by rescue with exogenous polyamines. Cytostasis was induced in L1210 cells treated for 12 days with 10 microM AbeAdo; however, exposure to up to 40 microM AbeAdo did not induce cytostasis in R20 cells. Putrescine levels were elevated and spermine levels were depleted in both treated L1210 and treated R20 cells. Spermidine was depleted in treated L1210 cells but was only partly reduced in treated R20 cells. AdoMetDC activity was below the limit of detection in treated L1210 cells but, although greatly reduced, could be measured in the treated R20 cells. The resistance of the R20 cells to the effects of AbeAdo on cell growth and spermidine depletion correlated with reduced AbeAdo accumulation by R20 cells. In the absence of spermidine synthesis, unhypusinated eukaryotic translation initiation factor 5A (eIF-5A) accumulated in AbeAdo-treated L1210 cells. There was no detectable accumulation of unhypusinated eIF-5A in R20 cells. Unhypusinated eIF-5A accumulated during AbeAdo treatment was depleted in L1210 cells rescued by exogenous spermidine. These findings are consistent with the hypothesis that AbeAdo-induced cytostasis is due to the loss of hypusinated eIF-5A. However, spermine was able to rescue AbeAdo-treated L1210 cells without significantly reducing the unhypusinated eIF-5A accumulated during AbeAdo treatment, suggesting that only a small amount of the unmodified protein must be hypusinated to restore cell growth.

scholarly journals eIF4E is a central node of an RNA regulon that governs cellular proliferation

2006 ◽  
Vol 175 (3) ◽  
pp. 415-426 ◽  
Author(s):  
Biljana Culjkovic ◽  
Ivan Topisirovic ◽  
Lucy Skrabanek ◽  
Melisa Ruiz-Gutierrez ◽  
Katherine L.B. Borden
Keyword(s):  
Cell Cycle ◽  
Messenger Rna ◽  
Cell Cycle Progression ◽  
Cellular Proliferation ◽  
Mrna Export ◽  
Nuclear Bodies ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Eukaryotic Translation ◽  
Eukaryotic Translation Initiation

This study demonstrates that the eukaryotic translation initiation factor eIF4E is a critical node in an RNA regulon that impacts nearly every stage of cell cycle progression. Specifically, eIF4E coordinately promotes the messenger RNA (mRNA) export of several genes involved in the cell cycle. A common feature of these mRNAs is a structurally conserved, ∼50-nucleotide element in the 3′ untranslated region denoted as an eIF4E sensitivity element. This element is sufficient for localization of capped mRNAs to eIF4E nuclear bodies, formation of eIF4E-specific ribonucleoproteins in the nucleus, and eIF4E-dependent mRNA export. The roles of eIF4E in translation and mRNA export are distinct, as they rely on different mRNA elements. Furthermore, eIF4E-dependent mRNA export is independent of ongoing RNA or protein synthesis. Unlike the NXF1-mediated export of bulk mRNAs, eIF4E-dependent mRNA export is CRM1 dependent. Finally, the growth-suppressive promyelocytic leukemia protein (PML) inhibits this RNA regulon. These data provide novel perspectives into the proliferative and oncogenic properties of eIF4E.

scholarly journals Identification of a regulatory subcomplex in the guanine nucleotide exchange factor eIF2B that mediates inhibition by phosphorylated eIF2.

1996 ◽  
Vol 16 (11) ◽  
pp. 6603-6616 ◽  
Author(s):  
W Yang ◽  
A G Hinnebusch
Keyword(s):  
Translation Initiation ◽  
Inhibitory Effect ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Alpha Subunit ◽  
Guanine Nucleotide ◽  
Regulatory Domain ◽  
Nucleotide Exchange ◽  
Guanine Nucleotide Exchange ◽  
Cell Extracts

Eukaryotic translation initiation factor 2B (eIF2B) is a five-subunit complex that catalyzes guanine nucleotide exchange on eIF2. Phosphorylation of the alpha subunit of eIF2 [creating eIF2(alphaP]) converts eIF2 x GDP from a substrate to an inhibitor of eIF2B. We showed previously that the inhibitory effect of eIF2(alphaP) can be decreased by deletion of the eIF2B alpha subunit (encoded by GCN3) and by point mutations in the beta and delta subunits of eIF2B (encoded by GCD7 and GCD2, respectively). These findings, plus sequence similarities among GCD2, GCD7, and GCN3, led us to propose that these proteins comprise a regulatory domain that interacts with eIF2(alphaP) and mediates the inhibition of eIF2B activity. Supporting this hypothesis, we report here that overexpression of GCD2, GCD7, and GCN3 specifically reduced the inhibitory effect of eIF2(alphaP) on translation initiation in vivo. The excess GCD2, GCD7, and GCN3 were coimmunoprecipitated from cell extracts, providing physical evidence that these three proteins can form a stable subcomplex. Formation of this subcomplex did not compensate for a loss of eIF2B function by mutation and in fact lowered eIF2B activity in strains lacking eIF2(alphaP). These findings indicate that the trimeric subcomplex does not possess guanine nucleotide exchange activity; we propose, instead, that it interacts with eIF2(alphaP) and prevents the latter from inhibiting native eIF2B. Overexpressing only GCD2 and GCD7 also reduced eIF2(alphaP) toxicity, presumably by titrating GCN3 from eIF2B and producing the four-subunit form of eIF2B that is less sensitive to eIF2(alphaP). This interpretation is supported by the fact that overexpressing GCD2 and GCD7 did not reduce eIF2(alphaP) toxicity in a strain lacking GCN3; however, it did suppress the impairment of eIF2B caused by the gcn3c-R104K mutation. An N-terminally truncated GCD2 protein interacted with other eIF2B subunits only when GCD7 and GCN3 were overexpressed, in accordance with the idea that the portion of GCD2 homologous to GCD7 and GCN3 is sufficient for complex formation by these three proteins. Together, our results provide strong evidence that GCN3, GCD7, and the C-terminal half of GCD2 comprise the regulatory domain in eIF2B.

scholarly journals eIF4E promotes nuclear export of cyclin D1 mRNAs via an element in the 3′UTR

2005 ◽  
Vol 169 (2) ◽  
pp. 245-256 ◽  
Author(s):  
Biljana Culjkovic ◽  
Ivan Topisirovic ◽  
Lucy Skrabanek ◽  
Melisa Ruiz-Gutierrez ◽  
Katherine L.B. Borden
Keyword(s):  
Cyclin D1 ◽  
Nuclear Export ◽  
Cellular Proliferation ◽  
Nuclear Bodies ◽  
Translation Initiation Factor ◽  
Cellular Growth ◽  
Initiation Factor ◽  
Eukaryotic Translation ◽  
Functional Sites ◽  
Eukaryotic Translation Initiation

The eukaryotic translation initiation factor eIF4E is a critical modulator of cellular growth with functions in the nucleus and cytoplasm. In the cytoplasm, recognition of the 5′ m7G cap moiety on all mRNAs is sufficient for their functional interaction with eIF4E. In contrast, we have shown that in the nucleus eIF4E associates and promotes the nuclear export of cyclin D1, but not GAPDH or actin mRNAs. We determined that the basis of this discriminatory interaction is an ∼100-nt sequence in the 3′ untranslated region (UTR) of cyclin D1 mRNA, we refer to as an eIF4E sensitivity element (4E-SE). We found that cyclin D1 mRNA is enriched at eIF4E nuclear bodies, suggesting these are functional sites for organization of specific ribonucleoproteins. The 4E-SE is required for eIF4E to efficiently transform cells, thereby linking recognition of this element to eIF4E mediated oncogenic transformation. Our studies demonstrate previously uncharacterized fundamental differences in eIF4E-mRNA recognition between the nuclear and cytoplasmic compartments and further a novel level of regulation of cellular proliferation.

scholarly journals Independent roles of eIF5A and polyamines in cell proliferation

2005 ◽  
Vol 385 (3) ◽  
pp. 779-785 ◽  
Author(s):  
Kazuhiro NISHIMURA ◽  
Kaori MUROZUMI ◽  
Akira SHIRAHATA ◽  
Myung Hee PARK ◽  
Keiko KASHIWAGI ◽  
...  
Keyword(s):  
Cell Proliferation ◽  
Cell Growth ◽  
Translation Initiation ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Deoxyhypusine Synthase ◽  
Eukaryotic Translation ◽  
Spermine Synthase ◽  
Polyamine Content ◽  
Eukaryotic Translation Initiation

To examine the roles of active hypusinated eIF5A (eukaryotic translation initiation factor 5A) and polyamines in cell proliferation, mouse mammary carcinoma FM3A cells were treated with an inhibitor of deoxyhypusine synthase, GC7 (N1-guanyl-1, 7-diaminoheptane), or with an inhibitor of ornithine decarboxylase, DFMO (α-difluoromethylornithine), or with DFMO plus an inhibitor of spermine synthase, APCHA [N1-(3-aminopropyl)-cyclohexylamine]. Treatment with GC7 decreased the level of active eIF5A on day 1 without affecting cellular polyamine content, and inhibition of cell growth occurred from day 2. This delay reflects the fact that eIF5A was present in excess and was very stable in these cells. Treatment with DFMO or with DFMO plus APCHA inhibited cell growth on day 1. DFMO considerably decreased the levels of putrescine and spermidine, and the formation of active eIF5A began to decrease when the level of spermidine fell below 8 nmol/mg of protein after 12 h of incubation with DFMO. The combination of DFMO and APCHA markedly decreased the levels of putrescine and spermine and significantly decreased the level of spermidine, but did not affect the level of active eIF5A until day 3 when spermidine level decreased to 7 nmol/mg of protein. The results show that a decrease in either active eIF5A or polyamines inhibits cell growth, indicating that eIF5A and polyamines are independently involved in cell growth.

scholarly journals Double-Stranded RNA-Activated Protein Kinase (PKR) Is Negatively Regulated by 60S Ribosomal Subunit Protein L18

1999 ◽  
Vol 19 (2) ◽  
pp. 1116-1125 ◽  
Author(s):  
Kotlo U. Kumar ◽  
Sri P. Srivastava ◽  
Randal J. Kaufman
Keyword(s):  
Protein Synthesis ◽  
Protein Kinase ◽  
Cell Growth ◽  
Ribosomal Subunit ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Cancer Tissue ◽  
Double Stranded Rna ◽  
Dsrna Binding

ABSTRACT The double-stranded RNA (dsRNA)-activated protein kinase (PKR) provides a fundamental control step in the regulation of protein synthesis initiation through phosphorylation of the alpha subunit of eukaryotic translation initiation factor 2 (eIF-2α), a process that prevents polypeptide chain initiation. In such a manner, activated PKR inhibits cell growth and induces apoptosis, whereas disruption of normal PKR signaling results in unregulated cell growth. Therefore, tight control of PKR activity is essential for regulated cell growth. PKR is activated by dsRNA binding to two conserved dsRNA binding domains within its amino terminus. We isolated a ribosomal protein L18 by interaction with PKR. L18 is a 22-kDa protein that is overexpressed in colorectal cancer tissue. L18 competed with dsRNA for binding to PKR, reversed dsRNA binding to PKR, and did not directly bind dsRNA. Mutation of K64E within the first dsRNA binding domain of PKR destroyed both dsRNA binding and L18 interaction, suggesting that the two interactive sites overlap. L18 inhibited both PKR autophosphorylation and PKR-mediated phosphorylation of eIF-2α in vitro. Overexpression of L18 by transient DNA transfection reduced eIF-2α phosphorylation and stimulated translation of a reporter gene in vivo. These results demonstrate that L18 is a novel regulator of PKR activity, and we propose that L18 prevents PKR activation by dsRNA while PKR is associated with the ribosome. Overexpression of L18 may promote protein synthesis and cell growth in certain cancerous tissue through inhibition of PKR activity.

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