Mimosine Arrests DNA Synthesis at Replication Forks by Inhibiting Deoxyribonucleotide Metabolism

Abstract

Mimosine has been reported to specifically prevent initiation of DNA replication in the chromosomes of mammalian nuclei. To test this hypothesis, the effects of mimosine were examined in several DNA replication systems and compared with the effects of aphidicolin, a specific inhibitor of replicative DNA polymerases. Our results demonstrated that mimosine inhibits DNA synthesis in mitochondrial, nuclear, and simian virus 40 (SV40) genomes to a similar extent. Furthermore, mimosine and aphidicolin were indistinguishable in their ability to arrest SV40 replication forks and mammalian nuclear chromosomal replication forks. In contrast to aphidicolin, mimosine did not inhibit DNA replication in lysates of mammalian cells supplied with exogenous deoxyribonucleotide triphosphate precursors for DNA synthesis. Mimosine also had no effect on initiation or elongation of DNA replication in Xenopus eggs or egg extracts containing high levels of deoxyribonucleotide triphosphates. In parallel with its inhibitory effect on DNA synthesis in mammalian cells, mimosine altered deoxyribonucleotide triphosphate pools in a manner similar to that reported for another DNA replication inhibitor that affects deoxyribonucleotide metabolism, hydroxyurea. Taken together, these results show that mimosine inhibits DNA synthesis at the level of elongation of nascent chains by altering deoxyribonucleotide metabolism.

p21-induced cycle arrest in G1 protects cells from apoptosis induced by UV-irradiation or RNA polymerase II blockage

“…Furthermore, p21 Waf1/Cip1 can be induced by a p53-independent pathway possibly involving perturbation of ribonucleotide pools. The drug mimosine is a non-protein amino acid which has been hypothesized to interact indirectly with ribonucleotide reductase by complexing iron ions and thereby blocking DNA synthesis by decreasing cellular dNTP concentrations (Gilbert et al, 1995). Cell cycle analysis of A431 cells treated with hydroxyurea, which depletes deoxyribonucleotide pools by speci®cally inhibiting ribonucleotide reductase (Elledge and Davis, 1990), showed an arrest in Sphase that di ers from the G 1 arrest induced by mimosine (Figure 7d).…”

The destruction box of human Geminin is critical for proliferation and tumor growth in human colon cancer cells

“…Cells were synchronized to G1-S by 0.4 mM mimosine (Sigma) for 24 h (Gilbert et al, 1995). To prepare the M-G1 phase cell lysates, the cells blocked for 24 h by nocodazole (200 ng/ml) were harvested after the 3 h of release.…”

Cell cycle re-entry following chemically-induced cell cycle synchronization leads to elevated p53 and p21 protein levels

“…Aphidicolin is a known inhibitor of DNA polymerases (Wang, 1991). Mimosine is a plant amino acid thought to block DNA synthesis by decreasing cellular dNTP concentrations through regulation of ribonucleotide reductase (Dai et al, 1994;Gilbert et al, 1995). Previously, many studies have used these agents to synchronize cells to examine cell cycle regulation of gene expression and protein activity.…”