A Mushroom Fruiting Body-Inducing Substance Inhibits Activities of Replicative DNA Polymerases

Abstract

We found and isolated two natural products in the extract from a basidiomycete,Ganoderma lucidum,as eukaryotic DNA polymerase inhibitors. The compounds were identified as cerebrosides, (4E,8E)-ND-2′-hydroxypalmitoyl-1-O-β-D-glucopyranosyl-9methyl-4,8-sphingadienine and (4E,8E)-N-D-2′-hydroxystearoyl-1-O-β-D-glucopyranosyl-9-methyl-4,8-sphingadienine, and were found to be identical to the mushroom fruiting body-inducing substances (FIS) reported. These cerebrosides selectively inhibited the activities of replicative DNA polymerases, especially the α-type, from phylogenetically broad eukaryotic species, whereas they hardly influenced the activities of DNA polymerase β, prokaryotic DNA polymerases, terminal deoxynucleotidyl transferase, HIV reverse transcriptase, RNA polymerase, deoxyribonuclease I, and ATPase. The inhibition of another replicative polymerase, the δ-type, was moderate. The inhibitions of the replicative polymerases were dose-dependent, and the IC50for animal or mushroom DNA polymerase α was achieved at approximately 12 μg/ml (16.2 μM) and for animal DNA polymerase δ at 57 μg/ml (77.2 μM). FIS is possibly a DNA polymerase inhibitor specific to the replicative enzyme group, and the fruiting body formation may be required for the suppression of the DNA replication or the vegetative growth of the mycelium.