Nucleic Acids Research Advance Access published online on October 21, 2009
Nucleic Acids Research, doi:10.1093/nar/gkp863
Genomics |
Novel recognition motifs and biological functions of the RNA-binding protein HuD revealed by genome-wide identification of its targets
1Cell Biology and Physiology, University of New Mexico HSC, Albuquerque, NM, USA, 2Translational Genomics (T-Gen), Phoenix, AZ, USA and 3Department of Neurosciences, University of New Mexico School of Medicine, 1 University of New Mexico, MSC08 4740, Albuquerque, NM 87131, USA
*To whom correspondence should be addressed. Tel: +1 505 272 1165; Fax: +1 505 272 8082; Email: nbizzozero{at}salud.unm.edu
Received May 22, 2009. Revised September 24, 2009. Accepted September 28, 2009.
HuD is a neuronal ELAV-like RNA-binding protein (RBP) involved in nervous system development, regeneration, and learning and memory. This protein stabilizes mRNAs by binding to AU-rich instability elements (AREs) in their 3' unstranslated regions (3' UTR). To isolate its in vivo targets, messenger ribonucleoprotein (mRNP) complexes containing HuD were first immunoprecipitated from brain extracts and directly bound mRNAs identified by subsequent GST-HuD pull downs and microarray assays. Using the 3' UTR sequences of the most enriched targets and the known sequence restrictions of the HuD ARE-binding site, we discovered three novel recognition motifs. Motifs 2 and 3 are U-rich whereas motif 1 is C-rich. In vitro binding assays indicated that HuD binds motif 3 with the highest affinity, followed by motifs 2 and 1, with less affinity. These motifs were found to be over-represented in brain mRNAs that are upregulated in HuD overexpressor mice, supporting the biological function of these sequences. Gene ontology analyses revealed that HuD targets are enriched in signaling pathways involved in neuronal differentiation and that many of these mRNAs encode other RBPs, translation factors and actin-binding proteins. These findings provide further insights into the post-transcriptional mechanisms by which HuD promotes neural development and synaptic plasticity.