A Molecular Circuit Composed of CPEB-1 and c-Jun Controls Growth Hormone-Mediated Synaptic Plasticity in the Mouse Hippocampus

Cytoplasmic polyadenylation element binding protein 1 (CPEB-1) resides at postsynaptic sites in hippocampal neurons in which it controls polyadenylation-induced translation. CPEB-1 knock-out (KO) mice display defects in some forms of synaptic plasticity and hippocampal-dependent memories. To identify CPEB-1-regulated mRNAs, we used proteomics to compare polypeptides in wild-type (WT) and CPEB-1 KO hippocampus. Growth hormone (GH) was reduced in the KO hippocampus, as were the GH signaling molecules phospho-JAK2 and phospho-STAT3. GH mRNA and pre-mRNA were reduced in the KO hippocampus, suggesting that CPEB-1 controls GH transcription. The transcription factor c-Jun, which binds the GH promoter, was also reduced in the KO hippocampus, as was its ability to coimmunoprecipitate chromatin containing the GH promoter. CPEB-1 binds c-Jun 3' untranslated region CPEs in vitro and coimmunoprecipitates c-Jun RNA in vivo. GH induces long-term potentiation (LTP) when applied to hippocampal slices from WT and CPEB-1 KO mice, but the magnitude of LTP induced by GH in KO mice is reduced. Pretreatment with GH did not reverse the LTP deficit observed in KO mice after theta-burst stimulation (TBS). Cordycepin, an inhibitor of polyadenylation, disrupted LTP induced by either GH application or TBS. Finally, GH application to hippocampal slices induced JAK2 phosphorylation in WT but not KO animals. These results indicate that CPEB-1 control of c-Jun mRNA translation regulates GH gene expression and resulting downstream signaling events (e.g., synaptic plasticity) in the mouse hippocampus.VoRSUNY DownstateN/

Quaking Regulates Hnrnpa1 Expression through Its 3′ UTR in Oligodendrocyte Precursor Cells

In mice, Quaking (Qk) is required for myelin formation; in humans, it has been associated with psychiatric disease. QK regulates the stability, subcellular localization, and alternative splicing of several myelin-related transcripts, yet little is known about how QK governs these activities. Here, we show that QK enhances Hnrnpa1 mRNA stability by binding a conserved 3′ UTR sequence with high affinity and specificity. A single nucleotide mutation in the binding site eliminates QK-dependent regulation, as does reduction of QK by RNAi. Analysis of exon expression across the transcriptome reveals that QK and hnRNP A1 regulate an overlapping subset of transcripts. Thus, a simple interpretation is that QK regulates a large set of oligodendrocyte precursor genes indirectly by increasing the intracellular concentration of hnRNP A1. Together, the data show that hnRNP A1 is an important QK target that contributes to its control of myelin gene expression