Dr. Christopher Steward Francklyn

Professor

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.

Key References:
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.

Key References:
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

Key Reference:
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.

Chris Francklyn and former CMB graduate Anand Minajigi.
Photos By: Rajan Chawla, UVM Medical Photography

BACKGROUND

Chris received his Ph.D from the University of California at Santa Barbara in 1988. From 1989-1991, he carried out postdoctoral studies with Paul Schimmel, then at M.I.T. He joined the University of Vermont in 1991. He is currently Professor in the Department of Biochemistry, and Adjunct Professor in the Department of Microbiology and Molecular Genetics. Chris also serves as one of the three co-directors of the University of Vermont undergraduate program in Biochemistry.

SELECTED PUBLICATIONS

Puffenberger EG, Jinks RN, Sougnez C, Cibulskis K, Willert RA, Achilly NP, Cassidy RP, Fiorentini CJ, Heiken KF, Lawrence JJ, Mahoney MH, Miller CJ, Nair DT, Politi KA, Worcester KN, Setton RA, Dipiazza R, Sherman EA, Eastman JT, Francklyn C , Robey-Bond S, Rider NL, Gabriel S, Morton DH, Strauss KA. Genetic mapping and exome sequencing identify variants associated with five novel diseases. PLoS One. 2012;7(1):e28936. Epub 2012 Jan 17

Farris M, Lague A, Manuelyan Z, Statnekov J, Francklyn C Altered nuclear cofactor switching in retinoic-resistant variants of the PML-RARα oncoprotein of acute promyelocytic leukemia. Proteins. 2012 Apr;80(4):1095-109. doi: 10.1002/prot.24010. Epub 2012 Jan 7.

Huang W, Bushnell EA, Francklyn CS , Gauld JW. The α-amino group of the threonine substrate as the general base during tRNA aminoacylation: a new version of substrate-assisted catalysis predicted by hybrid DFT. J Phys Chem A. 2011 Nov 17;115(45):13050-60. Epub 2011 Sep 26

Pasman Z, Robey-Bond S, Mirando AC, Smith GJ, Lague A, Francklyn CS. Substrate specificity and catalysis by the editing active site of Alanyl-tRNA synthetase from Escherichia coli. Biochemistry. 2011 Mar 8;50(9):1474-82. Epub 2011 Jan 31.

Minajigi A, Deng B, Francklyn CS .Fidelity escape by the unnatural amino acid β-hydroxynorvaline: an efficient substrate for Escherichia coli threonyl-tRNA synthetase with toxic effects on growth. Biochemistry. 2011 Feb 15;50(6):1101-9. Epub 2011 Jan 24.

Minajigi A, Francklyn CS . Aminoacyl transfer rate dictates choice of editing pathway in threonyl-tRNA synthetase. J Biol Chem. 2010 Jul 30;285(31):23810-7. Epub 2010 May 26.

Guth E, Farris M, Bovee M, Francklyn CS. Asymmetric amino acid activation by class II histidyl-tRNA synthetase from Escherichia coli. J Biol Chem. 2009 Jul 31;284(31):20753-62.

Minajigi A, Francklyn CS. RNA-assisted catalysis in a protein enzyme: The 2′-hydroxyl of tRNA(Thr) A76 promotes aminoacylation by threonyl-tRNA synthetase. Proc Natl Acad Sci U S A. 2008 Nov 18;105(46):17748-53.

Francklyn CS. DNA polymerases and aminoacyl-tRNA synthetases: shared mechanisms for ensuring the fidelity of gene expression. Biochemistry. 2008 Nov 11;47(45):11695-703.

Guth EC, Francklyn CS. Kinetic discrimination of tRNA identity by the conserved motif 2 loop of a class II aminoacyl-tRNA synthetase. Mol Cell. 2007 Feb 23;25(4):531-42.