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Design of hairpin ribozyme variants with improved activity for poorly processed substrates.

Authors
  • Drude, Irene
  • Strahl, Anne
  • Galla, Daniel
  • Müller, Oliver
  • Müller, Sabine
Type
Published Article
Journal
FEBS Journal
Publisher
Wiley (Blackwell Publishing)
Publication Date
Feb 01, 2011
Volume
278
Issue
4
Pages
622–633
Identifiers
DOI: 10.1111/j.1742-4658.2010.07983.x
PMID: 21199369
Source
Medline
License
Unknown

Abstract

Application of ribozymes for knockdown of RNA targets requires the identification of suitable target sites according to the consensus sequence. For the hairpin ribozyme, this was originally defined as Y⁻² N⁻¹ *G+¹ U+² Y+³ B+⁴, with Y = U or C, and B = U, C or G, and C being the preferred nucleobase at positions -2 and +4. In the context of development of ribozymes for destruction of an oncogenic mRNA, we have designed ribozyme variants that efficiently process RNA substrates at U⁻² G⁻¹ *G+¹ U+² A+³ A+⁴ sites. Substrates with G⁻¹ *G+¹ U+² A+³ sites were previously shown to be processed by the wild-type hairpin ribozyme. However, our study demonstrates that, in the specific sequence context of the substrate studied herein, compensatory base changes in the ribozyme improve activity for cleavage (eight-fold) and ligation (100-fold). In particular, we show that A+³ and A+⁴ are well tolerated if compensatory mutations are made at positions 6 and 7 of the ribozyme strand. Adenine at position +4 is neutralized by G⁶ →U, owing to restoration of a Watson-Crick base pair in helix 1. In this ribozyme-substrate complex, adenine at position +3 is also tolerated, with a slightly decreased cleavage rate. Additional substitution of A⁷ with uracil doubled the cleavage rate and restored ligation, which was lost in variants with A⁷, C⁷ and G⁷. The ability to cleave, in conjunction with the inability to ligate RNA, makes these ribozyme variants particularly suitable candidates for RNA destruction.

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