“The multiple faces of RNA binding proteins”

May 29th 2013

The multiple faces of RNA binding proteins 

The large and diverse group of RNA binding domains constitute the basic building blocks of proteins involved in mRNA metabolism. RNA Recognition Motifs (RRM) and CCCH-type zinc fingers are two of the most widely represented domains among RNA binding proteins. The RRM domain is a well-known module of around 80 residues with a βαββαβ fold, which exposes two conserved RNA binding motifs (RNP1 and RNP2) in the middle of the central β-sheet. The CCCH-type zinc fingers are much smaller (20 residues) and form an aperiodic fold with a Zn²⁺ ion on its centre. These basic units have, in general, low RNA binding affinity and specificity. To overcome this drawback, these domains frequently appear as multiple copies in RNA binding proteins, a strategy which is likely key for their biological function. An alternative approach to increase the versatility of these domains is to modify/expand their basic architecture. For example, RRM domains often contain N and/or C-terminal extensions of regular structural elements and some RRMs do not have conserved RNP1/RNP2 motifs, indeed some of them do not bind nucleic acids. In these work we study how this “lack of canonicity” in some RRM and zinc finger domains affects their structure and biological function in Saccharomyces cerevisiae mRNA metabolism. The studied systems contain novel structural elements, which are associated with unexpected specific biological roles in mRNA export and hnRNP formation.