6-Carboxyfluorescein and structurally similar molecules inhibit DNA binding and repair by O⁶-alkylguanine DNA alkyltransferase.

ABSTRACT: Human O⁶-alkylguanine-DNA alkyltransferase (AGT) repairs mutagenic O⁶-alkylguanine and O⁴-alkylthymine adducts in single-stranded and duplex DNAs. These activities protect normal cells and tumor cells against drugs that alkylate DNA; drugs that inactivate AGT are under test as chemotherapeutic enhancers. In studies using 6-carboxyfluorescein (FAM)-labeled DNAs, AGT reduced the fluorescence intensity by ∼40% at binding saturation, whether the FAM was located at the 5' or the 3' end of the DNA. AGT protected residual fluorescence from quenching, indicating a solute-inaccessible binding site for FAM. Sedimentation equilibrium analyses showed that saturating AGT-stoichiometries were higher with FAM-labeled DNAs than with unlabeled DNAs, suggesting that the FAM provides a protein binding site t

SUBMITTER: Melikishvili M 

PROVIDER: S-EPMC3217094 | biostudies-literature | 2011 Dec

REPOSITORIES: biostudies-literature