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Targeted cleavage of RNA molecules by human RNase P using minimized external guide sequences.
1Innovir Laboratories, New York, NY 10021, USA.
Antisense & Nucleic Acid Drug Development
|April 7, 1999
Summary
Human RNase P enzyme activity depends on external guide sequence (EGS) structure. Modifications to the D stem were tolerated, while changes to T stem and aminoacyl acceptor stem reduced cleavage efficiency.
Area of Science:
- Biochemistry
- Molecular Biology
- Enzymology
Background:
- RNase P is an essential endoribonuclease responsible for tRNA maturation.
- It processes tRNA-like structures composed of two separate strands: the substrate and the external guide sequence (EGS).
- Understanding the structural requirements of EGS is crucial for comprehending RNase P function.
Purpose of the Study:
- To investigate the impact of mutations and deletions in the external guide sequence (EGS) on human RNase P cleavage activity.
- To identify key structural domains within the EGS essential for substrate recognition and catalysis.
- To determine the binding affinities (Kd) of various bimolecular constructs with RNase P.
Main Methods:
- Systematic modification of EGS domains, including deletions and point mutations in the anticodon stem/loop, variable loop, T stem, aminoacyl acceptor stem, and D stem.
- Assessing the ability of modified EGS to induce cleavage of bimolecular constructs by human RNase P.
- Measuring the dissociation constants (Kd) for complex formation between EGS constructs and RNase P.
Main Results:
- Deletion of the anticodon stem/loop and variable loop did not significantly impair RNase P recognition.
- Modifications in the T stem and aminoacyl acceptor stem lengths decreased cleavage efficiency.
- Alterations within the D stem were more tolerated, and single nucleotide deletions in the T loop affected cleavage variably based on position.
- Kd values ranged from 0.2 nM to 28 nM, indicating strong binding affinities.
- Cleavage rates of 1 min(-1) were observed for both bimolecular EGS-target complexes and tRNA precursors.
Conclusions:
- The structural integrity of specific EGS domains, particularly the D stem, is critical for efficient human RNase P processing.
- RNase P exhibits distinct preferences for EGS structural features, influencing both binding and catalysis.
- This study provides valuable insights into the structure-function relationship of EGS in RNase P-mediated RNA processing.