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case western reserve university

BIOCHEMISTRY
 
 
Merrick

Dr. William C. Merrick

Professor

Pub Med:

Dr. William C. Merrick

The research goal of this laboratory is to identify all of the eukaryotic translation initiation factors and determine their sequential utilization in the initiation pathway. A secondary goal is to characterize how the initiation pathway is regulated and the different consequences depending on the exact point of regulation.

Current research is focusing on two major aspects of translation initiation, cap-dependent and cap-independent (or internal) initiation. Although much of the gross work has been determined using hemoglobin mRNA as a model mRNA, it has become clear that other elements influence both the regulation and mechanism of translation initiation in mammalian systems. Within the realm of cap-dependent translation, we are examining the influence of individual initiation factors on both overall affect on translation initiation and the affect of increased or decreased levels of initiation factors on start site selection in mRNAs containing in frame start sites which yield two proteins, one with a slightly longer N-terminal region than the other.

At the same time, we are also examining more closely the interaction of the mRNA specific initiation factors (eIF4A, eIF4B, eIF4F, eIF4H) with RNA. Both the characteristics of ideal RNAs for binding to the factors and ideal duplexes for unwinding are being examined.

As companion studies, yeast are being used to assess in vivo function of elements that influence internal initiation. Previous work has defined the Ure2p IRES (internal ribosome entry site) and has shown that IRES-mediated expression is specifically inhibited by the presence of eIF2A. We are currently trying to identify the minimal IRES element based upon the Ure2p IRES and determine how eIF2A regulates internal initiation. Preliminary data suggest that the regulation by eIF2A is controlled by both the amount of protein and by post-translational modification.

Selected References

  • Rogers, Jr., G. W., Komar, A. A., and Merrick, W. C. (2002) eIF4A: The Godfather of the DEAD-box Helicases. In Progress in Nucleic Acid Research and Molecular Biology. (K. Moldave, ed.) Academic Press, San Diego, p. 307-331.

  • Yang, H-S., Jansen, A. P., Komar, A. A., Zheng, X., Merrick, W. C., Costes, S., Lockett, S. J., Sonenberg, N. and Colburn, N. H. (2003) The transformation suppressor Pdcd4 is a novel eIF4A binding protein that inhibits translation. Mol. Cell. Biol. 23, 26-33.

  • Komar, A. A., Lesnik, T., Cullin, C., Merrick, W. C., Trachsel, H. and Altman, M. (2003) Internal initiation drives the synthesis of Ure2 protein lacking the prion domain and affects [URE3] propagation in yeast cells. EMBO J. 22, 1199-1209.

  • Merrick, W. C. (2003) Initiation of protein biosynthesis in eukaryotes. Bioc. Mol. Biol. Ed. 31, 378-385.

  • Merrick, W. C. (2004) Cap-dependent and cap-independent translation in eukaryotic systems. Gene 332, 1-11.

  • Komar, A. A., Gross, S. R., Barth-Baus, D., Strachan, R., Hensold, J. O., Kinzy, T. G. and Merrick, W. C. (2005) Novel characteristics of the biological properties of the yeast Saccharomyces cerevisiae initiation factor eIF2A. J. Biol. Chem. 280, 15601-15611.

  • Pisarev, A. V., Kolupaeva, V. G., Pisareva, V. P., Merrick, W. C., Hellen, C. U. and Pestova, T. V. (2006) Specific functional interactions of nucleotides at key -3 and +4 positions flanking the initiation codon with components of the mammalian 48S translation initiation complex. Genes Dev. 20, 624-636.

  • Robert, F., Gao, H. Q., Donia, M., Merrick, W. C., Hamann, M. T. and Pelletier, J. (2006) Chlorolissoclimides: New inhibitors of eukaryotic protein synthesis. RNA 12, 717-725.

  • Terenzi, F., Hui, D. J., Merrick, W. C. and Sen, G. C. (2006) Distinct induction patterns and functions of two closely related interferon-inducible human genes, ISG54 and ISG56. J. Biol. Chem. 281, 34064-34071.

  • Robert, F., Kapp, L. D., Khan, S. N., Acker, M., Kaufman, R. J., Merrick, W. C., Lorsch, J. R. and Pelletier, J. (2006) Translation initiation by the HCV IRES is refractory to reduced eIF2•GTP•Met-tRNAi ternary complex availability. Mol. Biol. Cell 17, 4632-4644.

  • Elroy-Stein, O. and Merrick, W. C. (2007) Translation initiation by cellular internal ribosome entry sites in Translational control in biology and medicine (ed. N. Sonenberg, J. W. H. Hershey and M. Matthews), Cold Spring Harbor Press, Cold Spring Harbor, New York, pages 155-172.

  • Dmitriev, S. E., Andreev D. E., Terenin, I. M., Olovnikov, I. A., Prassolov, V. S., Merrick, W. C. and Shatsky, I. N. (2007) Efficient translation initiation directed by the 900 nucleotide long and GC-rich 5’ UTR of the human retrotransposon LINE-1 mRNA is strictly cap-dependent rather than IRES-mediated. Mol. Cell. Biol. 27, 4685-4697.

  • Mathonnet, G., Fabian, M. R., Svitkin, Y. V., Parsyan, A., Huck, L., Murta, T., Biffo, S., Merrick, W. C., Darzynkiewicz, E., Pillai, R. S., Filipowicz, W., Duchaine, T. E. and Sonenberg, N. (2007) MicroRNA inhibition of translation initiation in vitro by targeting the cap-binding complex eIF4F. Science 317, 1764-1767

  • Merrick, W. C. and Barth-Baus, D. (2007) Use of reticulocyte lysates for mechanistic studies of eukaryotic translation initiation. Meth. Enzymol. 429, 1-21.

  • Reineke, L. C., Komar, A. A., Caprara, M. G. and Merrick, W. C. (2008) A small stem loop element directs internal initiation of the URE2 IRES in Saccharomyces cerevisiae. J. Biol. Chem. (in press).