HuD, a neuronal-specific RNA-binding protein, is a putative regulator of N-myc pre-mRNA processing/stability in malignant human neuroblasts.

N-myc gene copy numbers and transcription rates are similar in N (neuroblastic, tumorigenic) and S (non-neuronal, non-tumorigenic) neuroblastoma cells with chromosomally integrated amplified N-myc genes. However, N cells show significantly higher N-myc mRNA levels than S cells. Therefore, post-transcriptional control of N-myc gene expression must differ between these cell types. Since no differences in N-myc mRNA half-life were found between N and S cells from two cell lines, steady-state levels of N-myc pre-mRNA processing intermediates were analysed. Results suggest that the differences in N-myc expression arise primarily at the nuclear post-transcriptional level. The neuronal-specific RNA-binding Hu proteins are present in cytoplasmic and nuclear fractions of N cells and one of them, HuD, binds specifically to both exonic and intronic N-myc RNA sequences. In sense and antisense HuD-transfected N cells, there are coordinate changes in HuD and N-myc expression levels. Thus, we propose that HuD plays a role in the nuclear processing/stability of N-myc pre-mRNA in N-type neuroblastoma cells.