CELLULAR EFFECTS OF OLOMOUCINE, AN INHIBITOR OF CYCLIN-DEPENDENT KINASES

Olomoucine 2-hydroxyethylamino)-6-benzylamino-9-methylpurine) has been recently described as a competitive inhibitor (ATP-binding site) of t he cell cycle regulating p34(cdc2)/cyclin B, p33(cdk2)/cyclin A and p3 3(cdk2)/cyclin E kinases, the brain p33(cdk5)/p35 kinase and the ERK1/ MAP-kinase, The unusual specificity of this compound towards cell cycl e regulating enzymes suggests that it could inhibit certain steps of t he cell cycle. The cellular effects of olomoucine were investigated in a large variety of plant and animal models. This compound inhibits th e G1/S transition of unicellular algae (dinoflagellate and diatom). It blocks Fucus zygote cleavage and development of Laminaria gametophyte s. Stimulated Petunia mesophyl protoplasts are arrested in G1 by olomo ucine. By arresting cleavage it blocks the development of Calanus cope pod larvae. It reversibly inhibits the early cleavages of Caenorhabdit is elegans embryos and those of ascidian embryos. Olomoucine inhibits the serotonin-induced prophase/metaphase transition of clam oocytes; f urthermore, it triggers the release of these oocytes from their meioti c metaphase I arrest, and induces nuclei reformation. Olomoucine slows down the prophase/metaphase transition in cleaving sea urchin embryos , but does not affect the duration of the metaphase/anaphase and anaph ase/telophase transitions. It also inhibits the prophase/metaphase tra nsition of starfish oocytes triggered by various agonists. Xenopus ooc yte maturation, the in vivo and in vitro phosphorylation of elongation factor EF-1 are inhibited by olomoucine. Mouse oocyte maturation is d elayed by this compound, whereas parthenogenetic release from metaphas e II arrest is facilitated. Growth of a variety of human cell lines (r habdomyosarcoma cell lines Rh1, Rh18, Rh28 and Rh30; MCF-7, KB-3-1 and their adriamycin-resistant counterparts National Cancer Institute 60 human tumor cell lines comprising nine tumor types) is inhibited by ol omoucine. Cell cycle parameter analysts of the non-small cell lung can cer cell line MR65 shows that olomoucine affects G1 and S phase transi ts. Olomoucine inhibits DNA synthesis in interleukin-2-stimulated T ly mphocytes (CTLL-2 cells) and triggers a G1 arrest similar to interleuk in-2 deprivation. Both cdc2 and cdk2 kinases (immunoprecipitated from nocodazole- and hydroxyurea-treated CTLL-2 cells, respectively) are in hibited by olomoucine. Both yeast and Drosophila embryos were insensit ive to olomoucine. Taken together the results of this Noah's Ark appro ach show that olomoucine arrests cells both at the G1/S and the G2/M b oundaries, consistent with the hypothesis of a prevalent effect on the cdk2 and cdc2 kinases, respectively.