J. Biol. Chem., Vol. 259, Issue 8, 4904-4909, Apr, 1984
Aphidicolin, a specific inhibitor of DNA polymerase alpha, inhibits conversion of lanosterol to C-27 sterols in mouse L cells
DA Leonard and HW Chen
Aphidicolin, a fungal metabolite which is a specific inhibitor of DNA
polymerase alpha, inhibited the incorporation of [14C]acetate into
desmosterol in mouse L cells by 50% at a concentration of 8.8 microM. It
had no effect on acetate metabolism into fatty acids or CO2. The site of
inhibition was determined to be distal to the formation of mevalonic acid
since aphidicolin also inhibited the incorporation of [14C]mevalonolactone
into desmosterol but had no effect on the activity of
3-hydroxy-3-methylglutaryl-CoA reductase (EC 1.1.1.34) or the incorporation
of [14C]acetate into total nonsaponifiable lipids. High pressure liquid
chromotographic analysis of the distribution of radioactivity among the
nonsaponifiable lipids formed from [14C]acetate in the presence of
aphidicolin indicated an accumulation of lanosterol accompanied by a
proportional decrease in radiolabeled desmosterol and two of its
precursors, delta 5,7,24-cholestatrienol, and 4 alpha-methyl- delta
8,24-cholestadienol. In cells exposed to aphidicolin, lanosterol
accumulation was rapid (15 min) and reversible after a 3-h exposure when
cells were rinsed and fresh medium added. It was concluded that aphidicolin
inhibits the conversion of lanosterol to C-27 sterols. Although the exact
mechanism of this inhibition has not yet been determined, addition of
aphidicolin to 20,000 X g supernatant fractions of mouse liver homogenates
inhibited the incorporation of [14C]mevalonolactone into cholesterol in a
concentration-dependent manner, suggesting that aphidicolin may act
directly on one or more of the enzymatic steps involved in lanosterol
demethylation. The ubiquitous occurrence of an aphidicolin binding site on
eukaryotic DNA alpha polymerases and the inhibitory action of aphidicolin
at a proposed secondary regulatory site in sterol biosynthesis (lanosterol
metabolism) suggest that a naturally occurring compound may exist which can
regulate both DNA replication and cholesterogenesis.
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Reddit 
Technorati What's this?
