7-deaza-2--deoxyguanosine and 8-hydroxyguanine

Cellular DNA continuously suffers various types of damage, and unrepaired damage increases disease progression risk. 8-Oxo-2'-deoxyguanine (8-oxo-dG) is excised by repair enzymes, and their analogues are of interest as inhibitors and as bioprobes for study of these enzymes. We have developed 8-halogenated-7-deaza-2'-deoxyguanosine derivatives that resemble 8-oxo-dG in that they adopt the syn conformation. In this study, we investigated their effects on Fpg (formamidopyrimidine DNA glycosylase) and hOGG1 (human 8-oxoguanine DNA N-glycosylase 1). Relative to 8-oxo-dG, Cl- and Br-deaza-dG were good substrates for Fpg, whereas they were less efficient substrates for hOGG1. Kinetics and binding experiments indicated that, although hOGG1 effectively binds Cl- and Br-deaza-dG analogues with low Km values, their lower kcat values result in low glycosylase activities. The benefits of the high binding affinities and low reactivities of 8-oxo-dG analogues with hOGG1 have been successfully applied to the competitive inhibition of the excision of 8-oxoguanine from duplex DNA by hOGG1.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Base Sequence; Deoxyguanosine; DNA; DNA Glycosylases; DNA Repair; DNA-Formamidopyrimidine Glycosylase; Enzyme Inhibitors; Guanine; Halogenation; Humans; Kinetics; Models, Molecular; Protein Conformation