HnRNP Q suppresses polyglutamine aggregation by reducing Vaccinia-related kinase 2 mRNA stability

Abstract

Huntington’s disease (HD) is a progressive neurodegenerative disorder caused by a CAG trinucleotide repeat expansion in the huntingtin (HTT) gene, which encodes a polyglutamine tract in the HTT protein. Misfolding of proteins containing abnormal expansions of polyglutamine (polyQ) repeats is associated with cytotoxicity in HD. We have previously shown that vaccinia-related kinase 2 (VRK2) downregulates chaperonin TRiC protein levels through the ubiquitin-proteasome system by recruiting the E3 ligase COP1 and by destabilizing USP25 which is deubiquiting enzyme. Here we found that basal level of VRK2 in neuronal cells is regulated by post-transcriptional regulation. HnRNP Q specifically binds to 3’UTR of VRK2 mRNA in neuronal cells and reduces its stability. We report a dramatic increase polyglutamine aggregation by reducing hnRNP Q level. Thus, our results demonstrate that decreased brain hnRNP Q contributes to HD neurological phenotype and open new novel prognostic marker of HD.