ss-siRNAs allele selectively inhibit ataxin-3 expression: multiple mechanisms for an alternative gene silencing strategy |
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Authors: | Jing Liu Dongbo Yu Yuichiro Aiba Hannah Pendergraff Eric E. Swayze Walt F. Lima Jiaxin Hu Thazha P. Prakash David R. Corey |
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Affiliation: | 1.Departments of Pharmacology and Biochemistry, UT Southwestern Medical Center at Dallas, Dallas, TX 75390, USA and 2.Department of Medicinal Chemistry and Core Antisense Research, ISIS Pharmaceuticals, Carlsbad, CA 92010, USA |
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Abstract: | Single-stranded silencing RNAs (ss-siRNAs) provide an alternative approach to gene silencing. ss-siRNAs combine the simplicity and favorable biodistribution of antisense oligonucleotides with robust silencing through RNA interference (RNAi). Previous studies reported potent and allele-selective inhibition of human huntingtin expression by ss-siRNAs that target the expanded CAG repeats within the mutant allele. Mutant ataxin-3, the genetic cause of Machado–Joseph Disease, also contains an expanded CAG repeat. We demonstrate here that ss-siRNAs are allele-selective inhibitors of ataxin-3 expression and then redesign ss-siRNAs to optimize their selectivity. We find that both RNAi-related and non-RNAi-related mechanisms affect gene expression by either blocking translation or affecting alternative splicing. These results have four broad implications: (i) ss-siRNAs will not always behave similarly to analogous RNA duplexes; (ii) the sequences surrounding CAG repeats affect allele-selectivity of anti-CAG oligonucleotides; (iii) ss-siRNAs can function through multiple mechanisms and; and (iv) it is possible to use chemical modification to optimize ss-siRNA properties and improve their potential for drug discovery. |
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