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Overexpression of enzymes that repair endogenous damage to DNA
1DNA Repair Unit, Mutagenesis laboratory, Istituto Nazionale Ricerca Cancro, Genova, Italy. gfrosina@hp380.ist.unige.it
Abstract:
A significant contribution to human mutagenesis and carcinogenesis may come from DNA damage of endogenous, rather than exogenous, origin. Efficient repair mechanisms have evolved to cope with this. The main repair pathway involved in repair of endogenous damage is DNA base excision repair. In addition, an important contribution is given by O6-alkylguanine DNA alkyltranferase, that repairs specifically the miscoding base O6-alkylguanine. In recent years, several attempts have been carried out to enhance the efficiency of repair of endogenous damage by overexpressing in mammalian cells single enzymatic activities. In some cases (e.g. O6-alkylguanine DNA alkyltransferase or yeast AP endonuclease) this approach has been successful in improving cellular protection from endogenous and exogenous mutagens, while overexpression of other enzymatic activities (e.g. alkyl N-purine glycosylase or DNA polymerase beta) were detrimental and even produced a genome instability phenotype. The reasons for these different outcomes are analyzed and alternative enzymatic activities whose overexpression may improve the efficiency of repair of endogenous damage in human cells are proposed.
Insights
Enhancing DNA repair mechanisms is crucial for preventing mutagenesis and cancer. Overexpressing certain enzymes, like O6-alkylguanine DNA alkyltransferase, improves cellular protection, while others can cause genome instability.
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- Endogenous DNA damage contributes significantly to human mutagenesis and carcinogenesis.
- DNA base excision repair and O6-alkylguanine DNA alkyltransferase are key pathways for repairing endogenous DNA damage.
Purpose of the Study:
- To investigate the effects of overexpressing single enzymatic activities on DNA repair efficiency in mammalian cells.
- To analyze the reasons behind differential outcomes of enzyme overexpression on cellular protection and genome stability.
Main Methods:
- Overexpression of specific DNA repair enzymes (e.g., O6-alkylguanine DNA alkyltransferase, yeast AP endonuclease, alkyl N-purine glycosylase, DNA polymerase beta) in mammalian cells.
- Assessment of cellular protection against endogenous and exogenous mutagens.
- Evaluation of genome stability following enzyme overexpression.
Main Results:
- Overexpression of O6-alkylguanine DNA alkyltransferase and yeast AP endonuclease enhanced cellular protection.
- Overexpression of alkyl N-purine glycosylase and DNA polymerase beta proved detrimental, inducing genome instability.
Conclusions:
- The efficiency of enhancing DNA repair by enzyme overexpression varies significantly depending on the specific enzyme.
- Understanding the underlying mechanisms is crucial for identifying alternative enzymatic activities that can effectively improve endogenous DNA damage repair in human cells.