Methods and compositions for controlling efficacy of RNA silencing

• US 7,732,593 B2
• Filed: 06/13/2008
• Issued: 06/08/2010
• Est. Priority Date: 06/02/2003
• Status: Active Grant

• Current Assignee: University Of Massachusetts
• Original Assignee: University Of Massachusetts
• Inventors: Zamore, Phillip D., Tang, Guiliang
• Primary Examiner(s): SCHNIZER, RICHARD A
• Application Number:
  US12/139,072
• Publication Number:
  US 20090098614A1
• Time in Patent Office: 725 Days
• Field of Search: None
• US Class Current: 536/24.5
• CPC Class Codes: A61P 43/00 Drugs for specific purposes, not provided for in groups A61P1/00-A61P41/00
• CPC Class Codes: C12N 15/111 General methods applicable to biologically active non-coding nucleic acids
• CPC Class Codes: C12N 15/113 Non-coding nucleic acids modulating the expression of genes, e.g. antisense oligonucleotides; Antisense DNA or RNA; Triplex- forming oligonucleotides; Catalytic nucleic acids, e.g. ribozymes; Nucleic acids used in co-suppression or gene silencing when used in plants C12N15/8218
• CPC Class Codes: C12N 15/8218 Antisense, co-suppression, viral induced gene silencing [VIGS], post-transcriptional induced gene silencing [PTGS]
• CPC Class Codes: C12N 15/8261 with agronomic (input) traits, e.g. crop yield
• CPC Class Codes: C12N 2310/14 interfering N.A.
• CPC Class Codes: C12N 2310/335 Modified T or U
• CPC Class Codes: C12N 2320/50 Methods for regulating/modulating their activity
• CPC Class Codes: Y02A 40/146 Genetically Modified [GMO] plants, e.g. transgenic plants

Abstract

Based at least in part on an understanding of the mechanisms by which small RNAs (e.g., naturally-occurring miRNAs) mediate RNA silencing in plants, rules have been established for determining, for example, the degree of complementarity required between an RNAi-mediating agent and its target, i.e., whether mismatches are tolerated, the number of mismatches tolerated, the effect of the position of the mismatches, etc. Such rules are useful, in particular, in the design of improved RNAi-mediating agents which allow for more exact control of the efficacy of RNA silencing.

Claims

1. A method of enhancing RNA silencing activity of an RNAi agent in a mammalian cell or a plant cell comprising:

(i) selecting a target sequence in an mRNA expressed in the mammalian or plant cell; and

(ii) synthesizing an RNAi agent comprising an antisense strand that is complementary to the target sequence, wherein three, four or five nucleotides within 5 or fewer nucleotides from the 3′

end of the antisense strand are substituted with a nucleotide which does not form a Watson-Crick base pair when the antisense strand is base paired with the target sequence, such that the RNA silencing activity of the RNAi agent is enhanced.

2. The method of claim 1, wherein the RNAi agent is small interfering RNA (siRNA).

3. The method of claim 1, wherein the RNAi agent is a micro RNA (miRNA).

4. The method of claim 3, wherein the RNAi agent is a plant miRNA.

5. The method of claim 3, wherein the RNAi agent is an animal miRNA.

6. The method of claim 1, wherein the RNAi agent is chemically synthesized.

7. The method of claim 1, wherein the RNAi agent is enzymatically synthesized.

8. The method of claim 1, wherein the RNAi agent is formulated to facilitate entry of the agent into the cell.

9. The method of claim 1, wherein the RNAi agent is derived from an engineered precursor.

10. The method of claim 9, wherein the engineered precursor is a miRNA precursor (pre-miRNA).

11. The method of claim 10, wherein the pre-miRNA is encoded by a vector.

12. The method of claim 9, wherein the engineered precursor is a primary miRNA transcript (pri-miRNA).

13. The method of claim 12, wherein the pri-miRNA is encoded by a vector.

14. The method of claim 9, wherein the engineered precursor is a small hairpin RNA (shRNA) comprising a stem portion comprising the antisense strand.

15. The method of claim 14, wherein the shRNA is encoded by a vector.

16. The method of claim 1, wherein the cell is a mammalian cell.

17. The method of claim 1, wherein the cell is a human cell.

18. The method of claim 1, wherein the cell is a plant cell.

19. The method of claim 1, wherein the mRNA specifies the amino acid sequence of a cellular protein.

20. The method of claim 1, wherein the mRNA specifies the amino acid sequence of an extracellular protein.

21. The method of claim 1, wherein the mRNA specifies the amino acid sequence of a pathogen-associated protein.

22. The method of claim 21, wherein the pathogen-associated protein is a viral protein.

23. The method of claim 21, wherein the pathogen-associated protein is expressed by a host of a pathogen.

24. The method of claim 1, wherein the mRNA specifies the amino acid sequence of an endogenous protein.

25. The method of claim 1, wherein the mRNA specifies the amino acid sequence of a heterologous protein expressed in a recombinant cell or a genetically altered organism.

26. The method of claim 1, wherein the mRNA specifies the amino acid sequence of a protein encoded by a transgene.

27. The method of claim 1, wherein the mRNA specifies the amino acid sequence of a protein encoded by a pathogen which is capable of infecting a cell or an organism from which the cell is derived.

28. The method of claim 1, wherein each of three nucleotides within 5 or fewer nucleotides from the 3′

end of the antisense strand are substituted with a nucleotide which does not form a Watson-Crick base pair.

29. The method of claim 1, wherein each of four nucleotides within 5 or fewer nucleotides from the 3′

end of the antisense strand are substituted with a nucleotide which does not form a Watson-Crick base pair.

30. The method of claim 1, wherein each of five nucleotides within 5 or fewer nucleotides from the 3′

end of the antisense strand are substituted with a nucleotide which does not form a Watson-Crick base pair.