Translation initiation factors

Two initiation factors, eIF-3 and elF-lA, bind to the newly dissociated 40S ribosomal subunit. This delays its reassociation with the 60S subunit and allows other translation initiation factors to associate with the 40S subunit. 

Alone, P. V., and Dever, T. E. (2006). Direct binding of translation initiation factor eIF2gamma-G domain to its GTPase-activating and GDP—GTP exchange factors eIF5 and eIF2B epsilon. J. Biol. Client. 281, 12636—12644. 

Anthony, T. G., Fabian, J. R., Kimball, S. R., and Jefferson, L. S. (2000). Identification of domains within the epsilon-subunit of the translation initiation factor eIF2B that are necessary for guanine nucleotide exchange activity and eIF2B holoprotein formation. Biochim. Biophys. Acta 1492, 56—62. 

Bieniossek, C., Schutz, P., Bumann, M., Limacher, A., Uson, I., and Baumann, U. (2006). The crystal stmcture of the carboxy-terminal domain of human translation initiation factor eIF5. /. Mol. Biol. 360, 457—465. 

Boesen, T., Mohammad, S. S., Pavitt, G. D., and Andersen, G. R. (2004). Structure of the catalytic fragment of translation initiation factor 2B and identification of a critically important catalytic residue. /. Biol. Chem. 279, 10584—10592. 

Gomez, E., and Pavitt, G. D. (2000). Identification of domains and residues within the epsilon subunit of eukaryotic translation initiation factor 2B (eIF2Bepsilon) required for guanine nucleotide exchange reveals a novel activation function promoted by eIF2B complex formation. Mol. Cell Biol. 20, 3965—3976. 

In Vivo Deletion Analysis of the Architecture of a Multiprotein Complex of Translation Initiation Factors... 

Asano, K., Phan, L., Anderson, J., and Hinnebusch, A. G. (1998). Complex formation by all five homologues of mammalian translation initiation factor 3 subunits from yeast Saccha-romyces cerevisiae. J. Biol. Ghent. 273, 18573—18585. 

Danaie, P., Wittmer, B., Altmann, M., and Trachsel, H. (1995). Isolation of a protein complex containing translation initiation factor Prtl from Saccharomyces cerevisiae. J. Biol. Ghent. 270, 4288-4292. 

Naranda, T., MacMillan, S. E., and Hershey, J. W. B. (1994). Purified yeast translational initiation factor eIF-3 is an RNA-binding protein complex that contains the PRT1 protein. J. Biol. Chem. 269, 32286—32292. 

Singh, C. R., Curtis, C., Yamamoto, Y., Hall, N. S., Kruse, D. S., He, H., Hannig, E. M., and Asano, K. (2005). Eukaryotic translation initiation factor 5 is critical for integrity of the scanning preinitiation complex and accurate control of GCN4 translation. Mol. Cell. Biol. 25, 5480-5491. 

Valasek, L., Nielsen, K. H., Zhang, F., Fekete, C. A., and Hinnebusch, A. G. (2004). Interactions of Eukaryotic Translation Initiation Factor 3 (eIF3) Subunit NIPl/c with elFl and eIF5 promote preinitiation complex assembly and regulate start codon selection. Mol. Cell. Biol. 24, 9437-9455. 

The discovery of Green Fluorescent Protein (GFP) and the development of technology that allows specific proteins to be tagged with GFP has fundamentally altered the types of question that can be asked using cell biological methods. It is now possible not only to study where a protein is within a cell, but also feasible to study the precise dynamics of protein movement within living cells. We have exploited these technical developments and applied them to the study of translation initiation factors in yeast, focusing particularly on the... 

Genes of interest can be tagged at either the N or C terminal end. The decision to tag a protein at either the N or the C terminal depends upon the properties of the protein of interest. In our case, all the eukaryotic translation initiation factors were tagged C terminally to allow the endogenous promoter to influence the expression of the tagged protein. 

In studying the localization of eukaryotic translation initiation factors, we made use of the FR AP technique to determine whether the localized regions of eIF2/eIF2B represented dynamic centers of these proteins (Campbell et ah, 2005). 

An obvious extension of studies aimed at investigating the localization of translation initiation factors is an analysis of the localization of specific RNA species. For instance, with respect to the localization of eIF2, the localization of the initiator methionyl tRNA is an important consideration. 

McEwen, E., Kedersha, N., Song, B., Scheuner, D., Gilks, N., Han, A., Chen, J. J., Anderson, P., and Kaufman, R. J. (2005). Heme-regulated inhibitor (HRI) kinase-mediated phosphorylation of eukaryotic translation initiation factor 2 (eIF2) inhibits translation, induces stress granule formation, and mediates survival upon arsenite exposure. J. Biol. Chem. 280, 16925—16933. 

Table 6.1 Translation initiation factor requirements of internal ribosome entry site (IRES) elements... 

Kahvejian, A., Svitkin, Y. V., Sukarieh, R., M Boutchou, M. N., and Sonenberg, N. (2005). Mammalian poly(A)-binding protein is a eukaryotic translation initiation factor, which acts via multiple mechanisms. Genes Dev. 19, 104—113. 

Mader, S., Lee, H., Pause, A., and Sonenberg, N. (1995). The translation initiation factor eIF-4E binds to a common motif shared by the translation factor eIF-4gamma and the translational repressors 4E-binding proteins. Mol. Cell. Biol. 15, 4990-4997. 

Smirnova, J. B., Selley, J. N., Sanchez-Cabo, F., Carroll, K., Eddy, A. A., McCarthy, J. E., Hubbard, S. J., Pavitt, G. D., Grant, C. M., and Ashe, M. P. (2005). Global gene expression profiling reveals widespread yet distinctive translational responses to different eukaryotic translation initiation factor 2B-targeting stress pathways. Mol. Cell Biol. 25, 9340-9349. 

Delle Fratte, S., Piubelli, C., and Domenici, E. (2002). Development of a high-throughput scintillation proximity assay for the identification of C-domain translational initiation factor 2 inhibitors. J. Biomol. Screen. 7, 541—546. 

Moerke, N. J., Aktas, H., Chen, H., Cantel, S., Reibarkh, M. Y., Fahmy, A., Gross, J. D., Degterev, A., Yuan, J., Chorev, M., Halperin, J. A., and Wagner, G. (2007). Small-molecule inhibition of the interaction between the translation initiation factors eIF4E and eIF4G. Cell 128, 257-267. 

The application of forward chemical genetics to studies of translation provides an opportunity to identify small molecules that inhibit or stimulate this process without any underlying assumptions as to which step is most amenable to targeting by the chemical libraries under consideration. The opportunity exists to identify novel factors involved in translation, unravel new activities of known translation initiation factors, or characterize shortlived intermediates that are frozen by the small molecule inhibitor. We have undertaken a forward chemical genetic approach to identify small molecules that inhibit or stimulate translation in extracts prepared from Krebs-2 ascites cells (Novae et al., 2004). These screens have led to the identification of several novel inhibitors of translation initiation and elongation (Bordeleau et al., 2005, 2006 Robert et al., 2006a,b). 

Bordeleau, M. E., Matthews, J., Wojnar, J. M., Lindqvist, L., Novae, O., Jankowsky, E., Sonenberg, N., Northcote, P., Teesdale-Spitde, P., and Pelletier, J. (2005). Stimulation of mammalian translation initiation factor eIF4A activity by a small molecule inhibitor of eukaryotic translation. Proc. Natl. Acad. Sci. USA 102, 10460—10465. 

A novel functional human eukaryotic translation initiation factor 4G. Mol. Cell Biol. 18, 334-342. 

The cap-binding protein eIF4E promotes folding of a functional domain of yeast translation initiation factor eIF4Gl.J. Biol. Chem. 274, 21297—21304. 

Imataka, H., and Sonenberg, N. (1997). Human eukaryotic translation initiation factor 4G (eIF4G) possesses two separate and independent binding sites for eIF4A. Mol. Cell Biol. 17, 6940-6947. 

Pause, A., Methot, N., Svitkin, Y., Merrick, W. C., and Sonenberg, N. (1994). Dominant negative mutants of mammalian translation initiation factor eIF-4A define a critical role for eIF-4F in cap-dependent and cap-independent initiation of translation. EMBO J. 13, 1205-1215. 

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