The effect of mevalonic acid deprivation on enzymes of DNA replication in cells emerging from quiescence

Abstract

We have investigated the biochemical basis of the mevalonate dependence of DNA replication. Stimulating quiescent rat hepatoma cells to proliferate in the presence of compactin, an inhibitor of mevalonate synthesis, prevented DNA replication in as many as 80% of these cells. The percentage of cells that failed to replicate DNA increased with the increased duration of quiescence. Aphidicolin-sensitive DNA polymerase and ornithine decarboxylase activities were selectively decreased in compactin-treated cells, whereas RNA and protein synthesis, the level of dihydrofolate reductase and aphidicolin-resistant DNA polymerase activity were unaffected. Adding putrescine, the product of ornithine decarboxylase and the precursor of other polyamines, did not restore DNA replication. Our results demonstrate that the decreased activities of at least two DNA-replication enzymes are among the proximal causes of the failure of mevalonate-deprived cells to synthesize DNA. More importantly, our data indicate that a mevalonate-dependent factor(s) is progressively depleted during quiescence, and that inability to resynthesize this factor(s) may be the ultimate cause of the failure of resting cells to replicate DNA when stimulated to proliferate in the absence of mevalonate.

Differential cytotoxic effects of 7-dehydrocholesterol-derived oxysterols on cultured retina-derived cells: Dependence on sterol structure, cell type, and density

“…For the homogeneous and defined cells we utilized in the present study, then, the upregulation of cholesterol synthesis in response to the low levels of serum, and therefore potentially limiting amounts of exogenous cholesterol, in our culture media must also be considered as a possibility. If the recent immunohistochemical results of Zheng et al (2015) are indicative of the status of 661W cells, as surrogate cone photoreceptors, to synthesize cholesterol de novo , it might be expected that this cell line was not autonomous in this respect; however, as immortalized cells whose replicative potential has not been diminished in our hands— even without cholesterol supplementation (not shown)— then, by definition, they in fact must have an active cholesterol biosynthetic capacity (Silber et al, 1992). Taken together, our main consideration in incubating cultured cells with 7DHC-derived oxysterols was to effect their internalization, leading to the presence, accumulation to potentially toxic levels, metabolic and oxidative conversions, and subsequent biochemical activity of these molecules and their downstream products.…”

Statin and Bisphosphonate Induce Starvation in Fast-Growing Cancer Cell Lines

“…Mevalonate-deprivation related cell-cycle arrest and cell quiescence was first published more than 25 years ago [ 21 ]. A quiescence marker resulting from this pioneering study is the downregulation of the DNA polymerase A1 ( POLA1 ), which we also found downregulated in our study ( Table 1 ).…”

Variability in Cytochrome P450-Mediated Metabolism of Cardiovascular Drugs: Clinical Implications and Practical Attempts to Avoid Potential Problems

“…The exact mechanism(s) behind the muscle-related side effects of statins is not known, but the risk is clearly related to their systemic exposure [190,191]. As the enzyme HMG-CoA reductase mediates production of mevalonic acid, a precursor for crucial compounds in cell proliferation and coenzyme Q 10 (important for aerobic energy synthesis), the toxicity may reflect the direct inhibitory action of statins on HMGCoA reductase in skeletal muscle cells [190][191][192][193].…”