Jeannie Spagnolo, Ph.D.
Postdoctoral Fellow

Ph.D. Molecular Virology and Microbiology, Baylor College of Medicine, 2002.
B.S. Molecular Biology, Lehigh University, 1996.
D325 Fairchild
299 Campus Drive
Stanford CA 94305-5124
Research Summary

Experimental analysis of the quaternary structure of poliovirus RNA-dependent RNA polymerase (RdRP) indicates that the enzyme is capable of intermolecular polymerase-polymerase interactions at two sites, Interfaces I and II. These interfaces thus arrange pairs of RdRPs in two sets of head-to-tail fibers. Studies from our laboratory have demonstrated the propensity of the polymerase to oligomerize and form large structures resembling hollow tubes and sheet-like planar arrays. Mutant polymerases unable to participate in Interface I or Interface II interactions are unable to form these higher-order lattice structures, suggesting the importance of these interactions observed in the crystal structure for enzyme oligomerization in solution. It is not known whether poliovirus RdRPs deficient in either template RNA binding or in RNA catalysis can complement each other within a lattice to form a functional, processive enzyme complex in vitro or in infected cells. My project focuses on the ability of inactive or compromised polymerase mutants to complement each other functionally.

Several biochemical and structural properties of the poliovirus RdRP may hold true for other RdRP enzymes. Similar to poliovirus, it has been demonstrated that activity of the Hepatitis C virus RdRP is cooperative with respect to protein concentration, that two extensive interfaces for intermolecular polymerase-polymerase interaction exist within the molecule, and that the RdRP forms higher-order oligomeric structures observable by electron microscopy. These characteristics may apply to nonviral RdRPs as well. Recently, several putative RdRP genes were identified in the nematode Caenorhabditis elegans. These genes were identified based on sequence homology to known RdRP enzymes including that isolated from tomato plants. Mutations in the putative polymerase genes rendered affected worms resistant to RNA interference (RNAi). Another extension of my project is to determine whether structural and biochemical features are similar between these divergent RdRP enzymes.

Copyright 2006 - 2010. The Laboratory of Karla Kirkegaard, Ph.D. All rights reserved.