We utilized a custom-synthesized double-strand oligonucleotide containing a single O6-methylguanine (O6-MG) residue within a restriction endonuclease recognition site to determine O6-methylguanine-DNA-methyltransferase (O6-MGMT) activity in various tissue extracts prepared from Xiphophorus fish. The results suggest Xiphophorus fish O6-MGMT activity has many of the same characteristics as Escherichia coli and mammalian O6-MGMT's including rapid reaction kinetics consistent with stoichiometric removal of methyl groups, but exhibits a temperature optimum of 23°C. Results from protein extract activity assays indicate O6-MGMT activity patterns among four Xiphophorus tissues followed the order: brain ≥ testes > gill ≥ liver. In mammals, O6-MGMT activity is high in liver, while activity in brain is minimal (i.e. ≈9% of liver); however, we report that in the Xiphophorus fishes examined, brain tissue extracts exhibited much higher (≈six-fold) O6-MGMT activity levels than liver. Comparison of O6-MGMT activity between Xiphophorus species employed in tumor induction experiments did not indicate significant differences in ability to clear the pre-mutagenic O6-MG from the oligonucleotide substrate.
|Original language||English (US)|
|Number of pages||12|
|Journal||Mutation Research - Genetic Toxicology and Environmental Mutagenesis|
|State||Published - Jun 27 2001|
- DNA repair
ASJC Scopus subject areas
- Health, Toxicology and Mutagenesis