TOWARD A MECHANISTIC UNDERSTANDING OF THE MULTIFUNCTIONALITY OF RNA-BINDING PROTEINS: A (GLO)BAL PERSPECTIVE

Abstract

Post-transcriptional gene regulation requires specificity in molecular recognition. RNA binding proteins (RBPs), for example, face the challenge of precisely identifying motifs that control splicing, polyadenylation, localization, and translation. This challenge is compounded by the requirement for many RBPs to interact with numerous target RNAs and function in multiple aspects of RNA metabolism. Since the precise roles of RNA binding proteins in regulating gene expression are likely to be determined by their RNA binding specificity, it is important to have a clear understanding of how these proteins interact with their RNA targets as well as how these interactions transduce a particular biological response.

The Drosophila glorund (glo) gene provides an ideal model for studying these interactions, as Glo is a member of the hnRNP F/H family of proteins, which function in nearly all aspects of RNA metabolism. To gain insight into how Glo coordinates its multiple functions, we have determined the crystal structures of each of Glo’s three RNA binding domains and have identified mutations that differentially alter Glo’s ability to recognize known RNA substrates in vitro. By evaluating the effect of these mutations on Glo function in vivo, we demonstrate that Glo uses distinct RNA-binding surfaces to differentially regulate its targets. Additionally, using a bioinformatic approach based on known targets of Glo, we identify ~800 other potential RNA targets of Glo, suggesting that the functions of Glo may be much more widespread than we previously appreciated. Our data suggest a molecular mechanism for the regulation of diverse RNA targets by Glo that may be applied to understanding the functional diversity of other RNA-binding proteins. Moreover, it illustrates a general principle that RBPs may use different combinations of RNA recognition interfaces to regulate subsets of target RNAs that correlate with particular biological functions.