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[摘要]：The 3'-untranslated regions (3'-UTRs) of growth-associated protein 43 (GAP-43), which is crucial for neural development and axonal regeneration, are highly conserved among vertebrates. Previous studies in mammals have identified one U-rich cis element within GAP-43 3'-UTR and several trans factors that regulate its mRNA stability. However, much less is known in lower vertebrates. The Xenopus GAP-43 3'-UTR, despite its high similarity with those in higher vertebrates, contains unique CU-rich sequences, suggesting the existence of novel cis elements and trans factors. In current study, we isolated four proteins bound to GAP-43 3'-UTR from juvenile frog brain using affinity purification. Mass spectrometry identified Hu antigen D (HuD) and poly(C) binding protein 2 (alpha CP2) as the proteins forming 48- and 44-kDa ribonucleoprotein complexes, respectively. We validated the association between alpha CP2 and GAP-43 3'-UTR in vivo. After confirming the post-transcriptional effects of alpha CP2 on GAP-43 expression, we demonstrated that alpha CP2 directly inhibited the translation of GAP-43 gene, without affecting its mRNA stability. alpha CP2 overexpression led to decreased level of GAP-43 protein and significantly inhibited axonal outgrowth in primarily cultured neurons. Our study therefore provided insights on novel functions of alpha CP2 in vertebrate nervous system during development and new mechanisms of post-transcriptional regulation for GAP-43 gene. (C) 2012 Elsevier Inc. All rights reserved. |
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