Eukaryotic translation is believed to be regulated via the phosphorylation of specific eukaryotic initiation factors (eIFs), including one of the cap-binding complex proteins, eIF-4E. We show that in the yeast Saccharomyces cerevisiae, both eIF-4E and another cap-binding complex protein, p20, are phosphoproteins. The major sites of phosphorylation of yeast eIF-4E are found to be located in the N-terminal region of its sequence (Ser and Ser) and are thus in a different part of the protein from the main phosphorylation sites (Ser and Ser) proposed previously for mammalian eIF-4E. The most likely sites of p20 phosphorylation are at Ser and/or Ser. All of the major sites in the two yeast proteins are phosphorylated by casein kinase II in vitro. Casein kinase II phosphorylation of cap-complex proteins should therefore be considered as potentially involved in the control of yeast protein synthesis. Mutagenesis experiments revealed that yeast eIF-4E activity is not dependent on the presence of Ser or Ser. On the other hand, we observed variations in the amount of (phosphorylated) p20 associated with the cap-binding complex as a function of cell growth conditions. Our results suggest that interactions of yeast eIF-4E with other phosphorylatable proteins, such as p20, could play a pivotal role in translational control.

CiteULike

Complore

Connotea

Del.icio.us

Digg

Reddit

Technorati

This article has been cited by other articles:

				K. J. McAfee, D. T. Duncan, M. Assink, and A. J. Link Analyzing Proteomes and Protein Function Using Graphical Comparative Analysis of Tandem Mass Spectrometry Results Mol. Cell. Proteomics, August 1, 2006; 5(8): 1497 - 1513. [Abstract] [Full Text] [PDF]

				G. P. Cosentino, T. Schmelzle, A. Haghighat, S. B. Helliwell, M. N. Hall, and N. Sonenberg Eap1p, a Novel Eukaryotic Translation Initiation Factor 4E-Associated Protein in Saccharomyces cerevisiae Mol. Cell. Biol., July 1, 2000; 20(13): 4604 - 4613. [Abstract] [Full Text]

				S. Prieto, B. J. de la Cruz, and I. E. Scheffler Glucose-regulated Turnover of mRNA and the Influence of Poly(A) Tail Length on Half-life J. Biol. Chem., May 5, 2000; 275(19): 14155 - 14166. [Abstract] [Full Text] [PDF]

				J. T. Brown, X. Yang, and A. W. Johnson Inhibition of mRNA Turnover in Yeast by an xrn1 Mutation Enhances the Requirement for eIF4E Binding to eIF4G and for Proper Capping of Transcripts by Ceg1p Genetics, May 1, 2000; 155(1): 31 - 42. [Abstract] [Full Text]

				P. E. C. Hershey, S. M. McWhirter, J. D. Gross, G. Wagner, T. Alber, and A. B. Sachs The Cap-binding Protein eIF4E Promotes Folding of a Functional Domain of Yeast Translation Initiation Factor eIF4G1 J. Biol. Chem., July 23, 1999; 274(30): 21297 - 21304. [Abstract] [Full Text] [PDF]

				J. M. X. Hughes, M. Ptushkina, Md. M. Karim, N. Koloteva, T. von der Haar, and J. E. G. McCarthy Translational Repression by Human 4E-BP1 in Yeast Specifically Requires Human eIF4E as Target J. Biol. Chem., February 5, 1999; 274(6): 3261 - 3264. [Abstract] [Full Text] [PDF]

				J. E. G. McCarthy Posttranscriptional Control of Gene Expression in Yeast Microbiol. Mol. Biol. Rev., December 1, 1998; 62(4): 1492 - 1553. [Abstract] [Full Text] [PDF]

				J. de la Cruz, I. Iost, D. Kressler, and P. Linder The p20 and Ded1 proteins have antagonistic roles in eIF4E-dependent translation in Saccharomyces cerevisiae PNAS, May 13, 1997; 94(10): 5201 - 5206. [Abstract] [Full Text] [PDF]

				M. Ptushkina, I. Fierro-Monti, J. van den Heuvel, S. Vasilescu, R. Birkenhager, K. Mita, and J. E.G. McCarthy Schizosaccharomyces pombe Has a Novel Eukaryotic Initiation Factor 4F Complex Containing a Cap-binding Protein with the Human eIF4E C-terminal Motif KSGST J. Biol. Chem., December 20, 1996; 271(51): 32818 - 32824. [Abstract] [Full Text] [PDF]

				S. Vasilescu, M. Ptushkina, B. Linz, P. P. Müller, and J. E. G. McCarthy Mutants of Eukaryotic Initiation Factor eIF-4E with Altered mRNA Cap Binding Specificity Reprogram mRNA Selection by Ribosomes in Saccharomyces cerevisiae J. Biol. Chem., March 22, 1996; 271(12): 7030 - 7037. [Abstract] [Full Text] [PDF]

				H. Le, K. S. Browning, and D. R. Gallie The Phosphorylation State of Poly(A)-binding Protein Specifies Its Binding to Poly(A) RNA and Its Interaction with Eukaryotic Initiation Factor (eIF) 4F, eIFiso4F, and eIF4B J. Biol. Chem., June 2, 2000; 275(23): 17452 - 17462. [Abstract] [Full Text] [PDF]

				M. M. Karim, J. M. X. Hughes, J. Warwicker, G. C. Scheper, C. G. Proud, and J. E. G. McCarthy A Quantitative Molecular Model for Modulation of Mammalian Translation by the eIF4E-binding Protein 1 J. Biol. Chem., June 1, 2001; 276(23): 20750 - 20757. [Abstract] [Full Text] [PDF]