MODIFIED RNAI POLYNUCLEOTIDES AND USES THEREOF

摘要

The invention relates to improved RNAi constructs and uses thereof. The construct has a double stranded region of 19-49 nucleotides, preferably 25, 26, or 27 nucleotides, and preferably blunt-ended. The construct has selective minimal modifications to confer an optimal balance of biological activity, toxicity, stability, and target gene specificity. For example, the sense strand may be modified (e.g., one or both ends of the sense strand is/are modified by four 2'-O-methyl groups), such that the construct is not cleaved by Dicer or other RNAse III, and the entire length of the antisense strand is loaded into RISC. In addition, the antisense strand may also be modified by 2'-O-methyl group at the 2nd 5'-end nucleotide to greatly reduce off-target silencing. The constructs of the invention largely avoids the interferon response and sequence- independent apoptosis in mammalian cells, exhibits better serum stability, and enhanced target specificity.