Faculty & Research
- Contact Information
- Contact Tom Donahue by tfdonahu [at] indiana [dot] edu
- By telephone: unlisted
- JH 324A
Ph.D., Albert Einstein College of Medicine, 1979
The ribosomal scanning model has been proposed to account for molecular events that give rise to the initiation of eukaryotic protein synthesis. However, little information exists as to which gene products as part of the 40S ribosome preinitiation complex bind or interact with mRNA to mediate this process.
Our laboratory has established a genetic approach to identify these gene products. Mutations are made in the 5' untranslated region ot the HIS4mRNA in yeast that block either ribosomal binding of the mRNA, the ability of the 40S to scan the leader, or ribosomal recognition of the start site. These His-mutants are then analyzed in genetic reversion studies with emphasis on identifying His + revertants which are a result of a mutation in a gene that is unlinked to HIS4. These external suppressors represent mutations in genes that encode components of the preinitiation complex that now restore HIS4expression through an alteration of the normal translation initiation process. These genes are cloned and sequenced and used to develop probes to relate their encoded gene products to the biochemistry of the initiation process. In addition, these genes are examined to determine if their expression is subject to transcriptional, translational or post translational regulation in response to different physiological conditions.
Studies to date indicate that the AUG codon in yeast mRNA constitutes the signal for ribosomal start site selection. The initiator tRNA is what recognizes the AUG codon through a three base pair codon: anticodon interaction. This process is tightly controlled through the initiation factors; elF-2, elF-5 and the Sui1 gene product. The mechanism of control involves GTPase activity that provides a molecular switch for assuring that initiation only occurs when a three base-pair codon: anticodon interaction takes place. Currently, we are studying this mechanism and attempting to define the role of each factor during this reaction using genetics and biochemistry.
- Lo, H.-J., H.-K. Huang and T.F. Donahue. 1998. RNA polymerase I promoted HIS4expression yields uncapped polyadenylated mRNA that is unstable and inefficiently translated in Saccharomyces cerevisiae. Mol. Cell. Biol. 18:665-675.
- Huang, H.-K., H. Yoon, E. Hannig and T.F. Donahue. 1997. GTP hydrolysis controls stringent selection of the AUG start codon during translation initiation in S. cerevisiae. Genes & Dev. 11: 2396-2413.
- Naranda, T., S.E. MacMillan, T.F. Donahue and J.W.B. Hershey. 1996. SUI1/pl6 subunit is required for the activity of translational initiation factor elF-3 in S. cerevisiae. Mol. Cell. Biol. 16:2307-2313.
- Feng, L. and T.F. Donahue. 1994. Casein kinase 11 mediates multiple phosphorylation of elF-2 [alpha] (SU12) which is required for optimal elF-2 function in Saccharomyces cerevisiae. Mol. Cell Biol. 14:5139-5153.
- Feng, L. and T.F. Donahue. 1993. Genetic of translation initiation factors in Saccharomyces cerevisiae. In: Translational Regulation of Gene Expression II. Ilan, J. (ed.) Plenum Publ. Corp., NY, pp. 69-86.
- Dever, T., L. Feng, R. Wek, A.M. Cigan, T.F. Donahue and A. Hinnebush. 1992. Phosphorylation of initiation factor 2[alpha] by protein kinase Gen2 mediates gene-specific translational control of GCN4 in yeast. Cell 68:585-596.
- Yoon, H. and T.F. Donahue. 1992. The yeast translation initiation suppressor, suil,encodes a factor that functions during tRNA recognition of the start codon. Mol. Cell. Biol. 12:248-260.
- Cigan, A.M., E.K. Pabich, L. Feng, and T.E. Donahue. 1989. The yeast translation initiation suppresor sui2encodes elf 2 [alpha] and shares sequence identity with the human a-subunit. Proc. Natl. Acad. Sci. U.S.A. 86:2784-2788.
- Cigan, A.M., L. Feng, and T.F. Donahue. 1988. tRNA functions in directing the scanning ribosome to the start of translation. Science 242:93-97.
- Donahue, T. F., A.M. Cigan, E.K. Pabich, and B. Castilho-Valavicius. 1988. Mutations at a zing(II)finger motif in the yeast elF-[beta] gene alter ribosomal start site selection during the scanning proccss. Cell 54:621-632.