5′UTR-mediated regulation of Ataxin-1 expression

• Main Authors: Rachna Manek, Tiffany Nelson, Elizabeth Tseng, Edgardo Rodriguez-Lebron
• Format: Article
• Language: English
• Published: Elsevier 2020-02-01
• Series: Neurobiology of Disease
• Subjects: Spinocerebellar ataxia type 1; Ataxin-1; 5′untranslated region; Upstream AUG; Post-transcriptional gene regulation; Alternative splicing
• Online Access: http://www.sciencedirect.com/science/article/pii/S0969996119302323

Expression of mutant Ataxin-1 with an abnormally expanded polyglutamine domain is necessary for the onset and progression of spinocerebellar ataxia type 1 (SCA1). Understanding how Ataxin-1 expression is regulated in the human brain could inspire novel molecular therapies for this fatal, dominantly inherited neurodegenerative disease. Previous studies have shown that the ATXN1 3’UTR plays a key role in regulating the Ataxin-1 cellular pool via diverse post-transcriptional mechanisms. Here we show that elements within the ATXN1 5′UTR also participate in the regulation of Ataxin-1 expression. PCR and PacBio sequencing analysis of cDNA obtained from control and SCA1 human brain samples revealed the presence of three major, alternatively spliced ATXN1 5′UTR variants. In cell-based assays, fusion of these variants upstream of an EGFP reporter construct revealed significant and differential impacts on total EGFP protein output, uncovering a type of genetic rheostat-like function of the ATXN1 5′UTR. We identified ribosomal scanning of upstream AUG codons and increased transcript instability as potential mechanisms of regulation. Importantly, transcript-based analyses revealed significant differences in the expression pattern of ATXN1 5′UTR variants between control and SCA1 cerebellum. Together, the data presented here shed light into a previously unknown role for the ATXN1 5′UTR in the regulation of Ataxin-1 and provide new opportunities for the development of SCA1 therapeutics.