Talk abstracts
Talk on Friday 04:30-04:45pm submitted by Christopher Morgan
Structural insights into how the tandem RRMs of hnRNP A1 bind RNA stem loops
Christopher E. Morgan (Department of Chemistry, Case Western Reserve University), Jennifer L. Meagher (Life Sciences Institute, University of Michigan), Jeffrey D. Levengood (Department of Chemistry, Case Western Reserve University), Carrie Rollins (Department of Chemistry, Case Western Reserve University), James Delproposto, Jeanne A. Stuckey (Life Sciences Institute, University of Michigan), Blanton S. Tolbert (Department of Chemistry, Case Western Reserve University)
Abstract:
hnRNP A1 is an RNA binding protein involved in many biological functions. We present the first high-resolution crystal structure (1.92 Å) of the two-RRM binding domain of hnRNP A1, UP1, bound to a 5’-AGU-3’ RNA trinucleotide, representing sequence elements of several target stem loops. The structure shows that hnRNP A1 interacts specifically with the AG dinucleotide sequence through a nucleobase pocket formed between RRM1 and the inter-RRM linker where the RNA does not bind to RRM2. Using Isothermal Titration Calorimetry and Molecular Dynamics simulations, we show that two conserved salt bridge interactions at the inter-RRM interface (R75:D155 and R88:D157) stabilize the linker in a position to bind RNA with high affinity. We investigated the structural basis of UP1 binding HIV ESS3 by determining a SAXS-scored structural model of the complex, showing that UP1 binds to the apical loop of ESS3 using RRM1 and the inter-RRM linker only. Kinetic studies of the structural model revealed that mutations within the apical loop of ESS3 reduce binding affinities by slowing down the rate of association. The resulting data provides unique insights into how the tandem RRMs of hnRNP A1 cooperate to bind RNA stem loops.
Keywords: hnRNP A1, ESS3, HIV