Hu Jiaxin, Rigo Frank, Prakash Thazha P, Corey David R
1 Department of Pharmacology, UT Southwestern Medical Center at Dallas , Dallas, Texas.
2 Department of Biochemistry, UT Southwestern Medical Center at Dallas , Dallas, Texas.
Nucleic Acid Ther. 2017 Apr;27(2):87-94. doi: 10.1089/nat.2016.0655. Epub 2016 Dec 22.
Mutations within the chromosome 9 open reading frame 72 (c9orf72) gene are associated with both familial amyotrophic lateral sclerosis and frontotemporal dementia. The mutation leads to an expanded GGGGCC hexanucleotide repeat within the first intron of c9orf72 and an expanded CCCCGG repeat within a corresponding antisense transcript. Both the mutant intronic and antisense RNAs have been implicated in disease. We have previously reported that duplex RNAs complementary to the repeats can recognize disease-causing RNA and block detection of nuclear foci formed by the mutant transcripts. Here, we test the hypothesis that inhibition can also be achieved by single-stranded silencing RNAs (ss-siRNAs). ss-siRNAs are single-stranded antisense oligonucleotides (ASOs) that function through RNAi interference (RNAi) to silence gene expression. ss-siRNAs can block the expanded repeats within both intronic RNA and the antisense transcripts. Inhibition is more potent than by analogous duplex RNAs. Our data suggest that the potent effects on foci are caused by a combination of mechanisms including RNAi and direct binding of the ss-siRNA to the target transcripts. These findings reinforce the suggestion that ss-siRNAs combine the favorable properties of duplex RNA and single-stranded ASOs.
9号染色体开放阅读框72（c9orf72）基因内的突变与家族性肌萎缩侧索硬化症和额颞叶痴呆均相关。该突变导致c9orf72第一个内含子内的GGGGCC六核苷酸重复序列扩展，以及相应反义转录本内的CCCCGG重复序列扩展。突变的内含子RNA和反义RNA均与疾病有关。我们之前报道过，与这些重复序列互补的双链RNA能够识别致病RNA，并阻断对突变转录本形成的核灶的检测。在此，我们检验了单链沉默RNA（ss-siRNA）也能实现抑制作用的假说。ss-siRNA是通过RNA干扰（RNAi）发挥作用以沉默基因表达的单链反义寡核苷酸（ASO）。ss-siRNA能够阻断内含子RNA和反义转录本内的扩展重复序列。其抑制作用比类似的双链RNA更强。我们的数据表明，对核灶的强效作用是由包括RNAi以及ss-siRNA与靶转录本直接结合在内的多种机制共同导致的。这些发现进一步证明了ss-siRNA兼具双链RNA和单链ASO的有利特性。
