Andrew Feig Title Associate Professor Division Biochemistry Education B.S. Yale University 1990 Ph.D. MIT, 1995 Post-Doctoral Fellowship, 1995-1999, Univ. of Colorado, Boulder Office Chem 455 Phone (313)577-9229 E-Mail Group http://chem.wayne.edu/feiggroup

Our laboratory is interested in biological molecules that structurally rearrange as part of their normal activity.

Non-coding RNAs and the proteins with which they interact. Non-coding RNAs (ncRNAs) are involved in a variety of regulatory processes associated with mRNA stability and post-transcriptional gene regulation. We are using a variety of methodologies including structure mapping, CD spectroscopy, fluorescence, and microcalorimetry to probe the structural changes associated with the biology of ncRNAs. One system under study is DsrA, a ncRNA from E. coli involved in the cold shock response. Together with Hfq (Figure 1), a bacterial homolog of the Sm- and Lsm proteins, DsrA regulates RpoS translation. We have probed the different faces of Hfq and shown that they both bind RNAs but with different specificities. Hfq also interacts with a variety of proteins. We are looking at the way in which the RNAs bound to Hfq help to specify the protein components in this dynamic RNA-protein particle.

Thermodynamics of RNA Folding. RNA folding and RNA structural rearrangements are important determinants of the biological activity. We use CD, isothermal titration calorimetry (ITC) and differential scanning calorimetry (DSC) to probe these structural changes and the fundamental thermodynamics of RNA folding transitions. We have been looking extensively at heat capacity changes (ΔC_P), the temperature dependence of the ΔH. We are exploring the fundamental properties of this thermodynamic parameter, such as its physical origin in RNA folding, its dependence on oligonucleotide length and sequence, its dependence on ion condensation and water interactions, and the way it responds to divalent ion binding. We have found that the ΔC_P can be used, among other things, to reveal information about the residual structures in the “unfolded” state. Such structures have a major impact on isothermal folding.

Mechanistic Analysis of the Large Clostridial Cytotoxins. The laboratory is also investigating the mechanistic enzymology and biophysics of toxins A and B from Clostridium difficile, a common enteric bacterium. Infection with this organism is the primary cause of antibiotic-associated diarrhea (a condition that afflicts >3 million patients annually). Toxins A and B catalyze mono-glucosylation of the RhoA sub-family of small G-proteins, inducing apoptosis in the afflicted cells. We have cloned and expressed both the 66kD glucosyltransferase domain as well as the intact 300 kD holotoxin. We are using these materials to explore structural transitions required for translocation across cellular membranes during pathogenesis and substrate recognition.

Mikulecky, P.J. et al. E. coli Hfq Has Distinct Interaction Surfaces for DsrA, rpoS and polyA RNAs. Nat Struct & Mol Biol 11, 1206-1211 (2004).

Brescia, C.C., Mikulecky, P.J., Feig, A.L. & Sledjeski, D.D. Identification of the Hfq binding site on DsrA RNA: Hfq binds without altering DsrA secondary structure. RNA 9, 33-43 (2003).

Mikulecky, P.J., Takach, J.C. & Feig, A.L. Entropy-driven folding of an RNA helical junction: an isothermal titration calorimetric analysis of the hammerhead ribozyme. Biochemistry 43, 5870-81 (2004).

Mikulecky, P.J. & Feig, A.L. Heat capacity changes associated with DNA duplex formation: salt- and sequence-dependent effects. Biochemistry 45, 604-16 (2006).

Bhattacharyya, S., Kerzmann, A. & Feig, A.L. Fluorescent analogs of UDP-Glucose and their use in characterizing substrate binding by Toxin A from Clostridium difficile. Eur J Biochem 269, 3425-32. (2002).