During neuronal differentiation, use of an alternative splice site on the rat telomere repeat-binding factor 2 (TRF2) mRNA generates a short TRF2 protein isoform (TRF2-S) capable of derepressing neuronal genes. However, the RNA-binding proteins (RBPs) controlling this splicing event are unknown. Here, using affinity pull-down analysis, we identified heterogeneous nuclear ribonucleoproteins H1 and H2(HNRNPH) as RBPs specifically capable of interacting with the spliced RNA segment (exon 7) of Trf2 pre-mRNA. HNRNPH proteins prevent the production of the short isoform of Trf2 mRNA, as HNRNPH silencing selectively elevates TRF2-S levels. Accordingly, HNRNPH levels decline while TRF2-S levels increase during neuronal differentiation. In addition, CRISPR/Cas9-mediated deletion of hnRNPH2 selectively accelerates the NGF-triggered differentiation of rat pheochromocytoma cells into neurons. In sum, HNRNPH is a splicing regulator of Trf2 pre-mRNA that prevents the expression of TRF2-S, a factor implicated in neuronal differentiation. Neuronal differentiation is triggered by a change in TRF2 splice forms from full-length (FL) to short (S). Grammatikakis et al. find that the RNA-binding protein and splicing regulator HNRNPH prevents this switch, elevating TRF2-FL and inhibiting neurogenesis in rat. Accordingly, HNRNPH silencing leads to accumulation of TRF2-S and enhances neuronal differentiation.
Grammatikakis, I., Zhang, P., Panda, A. C., Kim, J., Maudsley, S., Abdelmohsen, K., … Gorospe, M. (2016). Alternative Splicing of Neuronal Differentiation Factor TRF2 Regulated by HNRNPH1/H2. Cell Reports, 15(5), 926–934. https://doi.org/10.1016/j.celrep.2016.03.080