The human CDK5R1 3'UTR contains distinct subregions affecting transcript stability

Human CDK5R1 encodes for p35, a neurone-specific activator of CDK5, which is involved in neuronal migration and differentiation during CNS development. CDK5R1 has been implicated in neurodegenerative disorders and proposed as a candidate gene for mental retardation. The remarkable size of CDK5R1 3’UTR suggests a role of this region in the control of CDK5R1 expression by post-transcriptional regulatory elements modulating mRNA stability or translation efficiency. Bioinformatic analysis showed a high conservation degree in mammals and predicted several AU-Rich Elements (AREs). CDK5R1 3’UTR was cloned in pGL4.71 at the 3’ end of the Renilla luciferase reporter gene to perform Dual Luciferase assays: the construct showed a decreased luciferase activity in six transfected cell lines. The quantitative analysis of luciferase mRNA suggests that CDK5R1 3’UTR affects mRNA stability. We identified five 3’UTR subregions reducing the luciferase activity in some instance with a cell line-dependent way. A region showed a significantly low halflife, suggesting an accelerated mRNA degradation. We also identified, by deletion analysis, a type I ARE displaying a stabilizing effect in two neuroblastoma cell lines. Our findings evince the presence of both destabilizing and stabilizing regulatory elements in CDK5R1 3’UTR. We are now attempting to identify, by REMSA and immunoprecipitation assays, stabilizing neuronal proteins that specifically bind the type I ARE, with the final aim of verifying the functionality of this element. The fine tuning of CDK5R1 expression by 3’UTR may play a role in CNS development and functioning, with potential implications in neurodegenerative and cognitive disorders.