HuD, a neuronal-specific RNA-binding protein, increases the in vivo stability of MYCN RNA

MYCN amplification and consequent deregulated expression plays a crucial role in determining the clinical behavior of neuroblastoma. Enhanced expression of MYCN confers growth potential to neuroblastoma cells, and a direct link between MYCN expression and the development of neuroblastoma has been demonstrated in transgenic mice studies. Although the molecular pathways underlying the regulation of MYCN have not been fully elucidated, post-transcriptional mechanisms appear to be important. Previously, we reported that an embryonic lethal abnormal vision-like (ELAV) protein binds with high specificity to at least two AU-rich elements within the MYCN 3'-untranslated region. In this study, we characterized the ability of cis-acting elements within the MYCN 3'-untranslated region to destabilize mRNA in cells and examined the functional consequences of its interactions with the ELAV protein HuD. We show that at least 4 cis-acting elements within the MYCN X-untranslated region are able to signal the degradation of stable heterologous mRNA. Ectopic overexpression of HuD dramatically inhibits RNA decay mediated by the full-length MYCN 3'-untranslated region and cis-acting destabilizing elements that harbor HuD binding sites in vivo. HuD may contribute to the malignant phenotype of neuroblastoma cells by stabilizing MYCN mRNA, thereby enhancing steady-state levels of expression of this oncogene.