Synergistic Regulation of MRNA by HuR and MiR-26/RISC in Neurons

The negative regulator of G-protein signalling 4 (Rgs4) is linked to several neurologic diseases, . schizophrenia, addiction, seizure and pain perception. Consequently, Rgs4 expression is tightly regulated, resulting in high mRNA and protein turnover. The post-transcriptional control of gene expression is mediated via RNA-binding proteins (RBPs) that interact with mRNAs in a combinatorial fashion. Here, we show that in neurons the RBP HuR reduces endogenous Rgs4 expression by destabilizing mRNA. Interestingly, in smooth muscle cells, is stabilized by HuR, indicating tissue-dependent differences in HuR function. Using RNA-based pulldown experiments, we identify the functional AU-rich element (ARE) within the 3'-UTR that is recognized and bound by HuR. Bioinformatic analysis uncovered that this ARE lies within a highly conserved area next to a miR-26 binding site. We find that the neuronal-enriched miR-26 negatively influences Rgs4 expression in neurons. Further, HuR and miR-26 act synergistically in fluorescent reporter assays. Together, our data suggest a regulatory mechanism, in which an RBP selectively destabilizes a target mRNA in cooperation with a miRNA and the RISC machinery.