Research: tRNA in Translation and Protein Synthesis
Structure and Function of Nucleic Acid Binding Proteins
General Description: My lab focuses on the relationship of protein structure to function, particularly in the context of protein nucleic acid interactions. To better understand how genes are regulated, both at the transcriptional and translational level, we are studying the structural and functional basis of protein-DNA and protein-RNA recognition using diverse experimental tools including enzymology, molecular biology, fluorescence, and x-ray crystallography. We hope to discover systematic principles of protein-nucleic acid recognition by these approaches, and then apply these to the design of proteins with novel therapeutic or biotechnological applications. Our work focuses on three main project areas:
Structure and Function of Aminoacyl-tRNA Synthetases
Project Description: In order to enter protein synthesis, all amino acids must first be joined to transfer RNAs, which serve as the adaptors of the genetic code. This reaction is catalyzed by the aminoacyl-tRNA synthetases (aaRSs). Our work on these enzymes currently focuses on the histidyl- and threonyl-tRNA synthetases, with some additional aaRSs in development. In particular, our studies focus on their structures, their mechanisms, and their exploitation as targets for both therapeutic and biotechnological applications.
Sankaranarayanan, R., Dock-Bregeon, A.-C, Rees, B., Bovee, M., Caillet, J., Romby, P., Francklyn, C. S., & Moras, D. (2000). Zinc mediated Amino Acid Discrimination by Threonyl-tRNA Synthetase. Nature Structural Biology. 7: 461-465.
Dock-Bregeon, A.-C., Sankaranarayan R., Romby, P., Caillet, J., Springer, M., Rees, B., Francklyn, C. S., Ehresmann, C., Moras, D. (2000) Transfer RNA mediated editing in the Class II Threonyl-tRNA Synthetase: The Class II Solution to the Double Discrimination Problem. Cell 103: 877-884.
Guth, E., Connolly, S.A, Bovee, M., & Francklyn, C.S. (2005) A substrate assisted concerted mechanism for aminoacylation of tRNAHis by histidyl-tRNA synthetase from Escherichia coli. Biochemistry. 44(10): 3785-3795.
Guth, E. & Francklyn, C.S. (2007) Kinetic Discrimination proofreading of tRNA identity by the conserved motif 2 loop of a class II aminoacyl-tRNA Synthetase. Molecular Cell 25:531-542.
Minajigi, A. & Francklyn, C.S. (2008) RNA assisted catalysis in a protein enzyme: the 2´ hydroxyl of tRNAThr A76 promotes aminoacylation by threonyl-tRNA synthetase . Proc. Natl. Acad. Sci. USA, in press.
Enzyme Paralogs: Alternative Functions with a Common Catalytic Fold
Project Description: An emerging theme in protein structure and enzymology is the recruitment of enzymes from one family to carry out novel functions that are distinct from those of the parent members. Several years ago we discovered a new ATP-PRTase family that incorporates a tRNA snythetase subunit as a regulatory domain. We are currently characterizing this enzyme and other tRNA synthetase-like proteins to discover new modes of translational control, as well as other functions distinct from protein synthesis.
Sissler, M., Delorme, C., Bond, J., Ehrlich, S.D., Renault, P., & Francklyn, C. (1999) An aminoacyl-tRNA synthetase progenitor with a catalytic role in amino acid biosynthesis. Proc. Natl. Acad. Sci. U.S.A. 96: 8985-8990.
Qui, H., Dong, J., Ha, C., Francklyn, C.S., Hinnebusch, A.G. (2001) The tRNA binding in GCN2 contains a dimerization domain that interacts with the kinase domain and is required for activation by uncharged tRNA. EMBO J.20: 1425-1438.
Champagne, K.S., Sissler, M., Larrabee, Y*., Doublie, S., and Francklyn, C.S. (2005) Activation of the hetero-octameric ATP phosphoribosyltransferase through subunint interface rearrangement by a tRNA synthetase paralog. Journal of Biological Chemistry. 280(40):34096-104.
Champagne, K.S., Piscitelli, E*., and Francklyn, C.S. (2006) Substrate Recognition by the Hetero-octameric ATP phosphoribosyltransferase from Lactococcus lactis. Biochemistry. 45(50) 14933-14943.
Nuclear Receptor Structure and Function in Cancer
Project Description: In our newest project, we are characterizing mutant versions of nuclear receptors that have acquired altered interactions with small molecule ligands (i.e. hormones and other regulatory molecules). These studies are focused on developing new methods for diagnosis and treatment of a variety of human
Farris, M. & Francklyn, C. S. (2007) Co-factor binding by all retinoic acid resistant mutants of the retinoic acid receptor a. from acute promyelocytic leukemia. In revision.