Karen S. Browning
Mechanism and Regulation of Eukaryotic Protein Synthesis
My research focuses on the initiation of protein synthesis in higher plants. We are seeking a molecular description of the process in which initiation factors (eIF4A, eIF4B, eIF4F, eIF3, eIF2 and PABP) select, prepare and bind messenger RNA to the 40S ribosome. Plants have a unique second form of eIF4F (eIF(iso)4F), and we are using a variety of methods (genetic knockouts, gene silencing, DNA arrays, etc.) to discover the function of this novel initiation factor. We are also interested in the features of messenger RNAs that make some messenger RNAs translate more efficiently than others and why plants need two forms of eIF4F. We are studying a plant viral RNA, satellite tobacco necrosis virus, that appears to use a region in the 3’ untranslated region (3’ UTR) to facilitate cap-independent translation by recruiting eIF4F. eIF4F is normally bound to the 5’ cap of mRNAs during initiation, so the use of the viral 3’ UTR to facilitate initiation at the 5’ end represents a novel mechanism. We are using a variety of techniques to study the interactions of initiation factors with each other and with messenger RNAs (expression of cloned factors, site-directed mutagenesis, crystallography, yeast three-hybrid system, fluorescence, etc.). From our studies we hope to gain a better understanding of the protein-protein and protein-RNA interactions that must occur for successful initiation of translation of a specific messenger RNA to occur.
Mayberry,L.K., Allen, M.L., Nitka, K.R., Campbell, L., Murphy, P.A. and Browning, K.S. (2011) Plant cap binding complexes eukaryotic initiation factors eIF4F and eIFiso4F: Molecular specificity of subunit binding. J. Biol. Chem. 286 (2011):42566-74.
Lellis AD, Allen ML, Aertker AW, Tran JK, Hillis DM, Harbin CR, Caldwell C, Gallie DR, Browning KS "Deletion of the eIFiso4G subunit of the Arabidopsis eIFiso4F translation initiation complex impairs health and viability" Plant Mol Biol 74 (2010): 249-63.
Dennis MD, Person MD, Browning KS "Phosphorylation of plant translation initiation factors by CK2 enhances the in vitro interaction of multifactor complex components" J Biol Chem. 284 (2009): 20615-28.
Dennis MD, Browning KS "Differential phosphorylation of plant translation initiation factors by Arabidopsis thaliana CK2 holoenzymes" J Biol Chem. 284 (2009): 20602-14.
Mayberry LK, Allen ML, Dennis MD, Browning KS "Evidence for variation in the optimal translation initiation complex: plant eIF4B, eIF4F, and eIF(iso)4F differentially promote translation of mRNAs" Plant Physiol 150 (2009): 1844-54.
Mayberry, L., Dennis, M.D., Allen, M.L., Nitka, K.A., Murphy, P.A., Campbell, L. and Browning, K.S. "Expression and Purification of Recombinant Wheat Translation Initiation Factors, eIF1, eIF1A, eIF4A, eIF4B, eIF4F, eIF(iso)4F and eIF5" Methods in Enzymology 430 (2007): 397-408.
Monzingo, A.F., Dhaliwal, S., Dutt-Chaudhuri, A., Lyon, A., Sadow, J., Hoffman, D.W., Robertus, J.D., and Browning, K.S "The Structure of Translation Initiation Factor eIF4E from Wheat Reveals a Novel Disulfide Bond" Plant. Physiology 143 (2007): 1504-1518.