Jon Gallant
phone: (206) 543-8235
fax: (206) 543-0754
Foege S232
Box 355065
jgallant [ a t ] uw.edu
Research:
Jon Gallant, a native of the planet Uranus, received his undergraduate degree at Haverford College during the late Pleistocene Epoch, and his Ph.D. (in Genetics and Biochemistry) somewhat later from Johns Hopkins University. He has been here at the University of Washington since the glaciers receded.
Gallant's laboratory played a major role in the analysis of the stringent control mechanism of bacteria, which links the pattern of transcription (and many aspects of metabolism) with the aminoacylation level of tRNA. Subsequently, they found that mutants defective in this control mechanism suffer increased errors in translation in response to imbalances in the aminoacyl-tRNA pools. This led to a variety of experimental approaches to the factors governing the accuracy of translation, and, more recently, of transcription.
Current experimental work focuses on the way in which reading frame is maintained or shifted as ribosomes translate the genetic code. The lab has analyzed sequence rules governing the tendency of ribosomes to shift either rightward or leftward when stalled at a "hungry" codon calling for an aminoacyl-tRNA in short supply. Among other things, they demonstrated how easy it is to convert a left-winger to a right-winger. More recently, they demonstrated that stalled ribosomes are capable of sliding over "hungry" codons and sequences downstream of them, and then continuing translation further on. In fact, the sliding (or "bypassing") phenomenon can be demonstrated in ordinary growing cells, and on a large variety of sequences. At this time, the lab is concentrating on defining the sequence rules which govern this phenomenon. Since ribosome frameshifting is employed in the translation of many plant and animal viruses (including retroviruses) and in a variety of bacterial and eukaryotic transposons, the basic rules governing its relationship to the genetic code may be of general interest.
Selected Publications:
Gallant, J. and Lindsley, D. 1993. Ribosome Frameshifting at Hungry Codons: Sequence Rules, Directional Specificity, and Possible Relationship to Mobile Element Behaviour. In: Biochemical Society Colloquium: "The New Biology of Protein Synthesis," Biochemical Journal 21:817-823.
Barak, Z., Lindsley, D. and Gallant, J. 1996. On the Mechanism of Leftward Frameshifting at Several Hungry Codons. J. Mol. Biol. 256:676-684.
Gallant, J.A. and Lindsley, D. 1998. Ribosomes can slide over and beyond "hungry" codons, resuming protein chain elongation many nucleotides downstream. Proceedings of the National Academy of Sciences (US) 95: 13771-13776.
Gallant, J., Lindsley, D., and Masucci, J. The Unbearable Lightness of Peptidyl-tRNA. Chapter 31 of The Ribosome: Structure, Function, Antibiotics, and Cellular Interactions. Garrett, R.A., Douthwaite, A. eds., Washington: ASM Press, 2000.
Lindsley, D., Gallant, J., and Guarneros, G. (2003) Ribosome bypassing elicited by tRNA depletion. Mol. Microbiol. 48: 1267-1274
Gallant, J., Bonthuis, P., and Lindsley, D. (2003) Evidence that the bypassing ribosome travels through the coding gap. Proc. Natl. Acad. Sci. USA 100: 13430-13435.
Gallant, J. et al. (2004) On the role of the starved codon and the takeoff site in ribosome bypassing in Escherichia coli. J. Mol. Biol. 342: 713-724.