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Sequence- and strand-specific cleavage in oligodeoxyribonucleotides and DNA containing 3'-thiothymidine
J S Vyle1, B A Connolly, D Kemp
1Robert Robinson Laboratories, Department of Chemistry, University of Liverpool, U.K.
Biochemistry
|March 24, 1992
Summary
Researchers developed a method for sequence-specific DNA cleavage using modified thymidine. This thiothymidine modification (T3's) resists EcoRV enzyme cleavage but can be chemically cleaved, enabling targeted strand modification.
Area of Science:
- Molecular Biology
- Biochemistry
- Synthetic Chemistry
Background:
- Restriction endonucleases like EcoRV are crucial tools for DNA manipulation.
- Site-specific DNA cleavage is essential for various molecular biology applications.
- Limitations exist in achieving strand-specific cleavage using enzymatic methods alone.
Purpose of the Study:
- To synthesize oligonucleotides and M13mp18 DNA containing a 3'-thiothymidine (T3's) modification.
- To investigate the resistance of the T3's modification to EcoRV restriction endonuclease.
- To explore chemical cleavage methods for the T3's linkage to achieve strand-specific DNA modification.
Main Methods:
- Automated DNA synthesis using a novel phosphorothioamidite reagent to incorporate T3's.
- Enzymatic cleavage assays with EcoRV on modified oligonucleotides and M13mp18 DNA.
- Chemical cleavage assays using silver ions (Ag+) and iodine on modified DNA strands.
Main Results:
- Oligonucleotides with T3's at the EcoRV site were resistant to EcoRV cleavage.
- Heteroduplexes showed cleavage only in the unmodified strand.
- The 3'-S-phosphorothiolate linkage was resistant to EcoRV but susceptible to chemical cleavage by Ag+ and iodine.
Conclusions:
- The 3'-thiothymidine modification confers resistance to EcoRV endonuclease activity.
- Chemical cleavage of the phosphorothiolate linkage allows for site-specific strand scission.
- This combined enzymatic and chemical approach enables sequence-specific cleavage of either DNA strand.