Inhibition of cell growth through inactivation of eukaryotic translation initiation factor 5A (eIF5A) by deoxyspergualin

2002 ◽  
Vol 363 (3) ◽  
pp. 761-768 ◽  
Author(s):  
Kazuhiro NISHIMURA ◽  
Yuji OHKI ◽  
Tomomi FUKUCHI-SHIMOGORI ◽  
Kaori SAKATA ◽  
Kan SAIGA ◽  
...  
Keyword(s):  
Cell Growth ◽  
Translation Initiation ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Deoxyhypusine Synthase ◽  
Eukaryotic Translation Initiation Factor ◽  
Free System ◽  
Eukaryotic Translation ◽  
Mechanism Of Inhibition ◽  
Eukaryotic Translation Initiation

The mechanism of inhibition of cell growth by deoxyspergualin was studied using mouse mammary carcinoma FM3A cells. Results of studies using deoxyspergualin analogues showed that both the guanidinoheptanate amide and glyoxyspermidine moieties of deoxyspergualin were necessary to cause inhibition of cell growth. When deoxyspergualin was added to the medium, there was a strong inhibition of cell growth and formation of active eukaryotic translation initiation factor 5A (eIF5A) at the third day of culture. There was also a marked decrease in cellular putrescine content and a small decrease in spermidine content. Accumulation of decapped mRNA, which is typically associated with eIF5A deficiency in yeast, was also observed. The inhibition of cell growth and the formation of active eIF5A was not reversed by addition of spermidine. The activity of deoxyhypusine synthase, the first enzyme in the formation of active eIF5A, was inhibited by deoxyspergualin in a cell-free system. These results, taken together, indicate that inhibition of active eIF5A formation is strongly involved in the inhibition of cell growth by deoxyspergualin.

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 Phosphorylation of Mammalian Eukaryotic Translation Initiation Factor 6 and Its Saccharomyces cerevisiae Homologue Tif6p: Evidence that Phosphorylation of Tif6p Regulates Its Nucleocytoplasmic Distribution and Is Required for Yeast Cell Growth

2003 ◽  
Vol 23 (17) ◽  
pp. 6187-6199 ◽  
Author(s):  
Uttiya Basu ◽  
Kausik Si ◽  
Haiteng Deng ◽  
Umadas Maitra
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Cell Growth ◽  
Translation Initiation ◽  
Translation Initiation Factor ◽  
Yeast Cells ◽  
Initiation Factor ◽  
Eukaryotic Translation Initiation Factor ◽  
Eukaryotic Translation ◽  
Antigenic Properties ◽  
Eukaryotic Translation Initiation

ABSTRACT The synthesis of 60S ribosomal subunits in Saccharomyces cerevisiae requires Tif6p, the yeast homologue of mammalian eukaryotic translation initiation factor 6 (eIF6). In the present work, we have isolated a protein kinase from rabbit reticulocyte lysates on the basis of its ability to phosphorylate recombinant human eIF6. Mass spectrometric analysis as well as antigenic properties of the purified kinase identified it as casein kinase I. The site of in vitro phosphorylation, which is highly conserved from yeast to mammals, was identified as the serine residues at positions 174 (major site) and 175 (minor site). The homologous yeast protein Tif6p was also phosphorylated in vivo in yeast cells. Mutation of Tif6p at serine-174 to alanine reduced phosphorylation drastically and caused loss of cell growth and viability. When both Ser-174 and Ser-175 were mutated to alanine, phosphorylation of Tif6p was completely abolished. Furthermore, while wild-type Tif6p was distributed both in nuclei and the cytoplasm of yeast cells, the mutant Tif6p (with Ser174Ala and Ser175Ala) became a constitutively nuclear protein. These results suggest that phosphorylatable Ser-174 and Ser-175 play a critical role in the nuclear export of Tif6p.

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