Trichomonas vaginalis: Dominant G2 Period and G2 Phase Arrest in a Representative of an Early Branching Eukaryotic Lineage

Abstract

Eukaryotic mitotic cell cycles have been extensively studied in yeasts and vertebrate cells but little is known about cell cycle mechanisms in early branches of the eukaryotic lineage. Trichomonas vaginalis represents one of the earliest branching eukaryotic lineages available for study. In contrast with most yeasts and vertebrate cells, the T. vaginalis G2 period was prolonged, comprising 50 to 58% of the cell population. Hydroxyurea, aphidicolin, and excess thymidine, all of which arrest yeasts and vertebrate cells at the G1/S phase boundary, had no effect on the T. vaginalis cell cycle, probably due to the known absence of synthetic pathways. The anti-microtubule mitotic inhibitors, colchicine and nocodazole, induced G2 phase synchrony. Metronidazole, a therapeutic reagent, also caused G2 phase arrest. These observations suggest that T. vaginalis is similar to yeasts and vertebrate cells in G2 and M phases, but the parasite's G1/S phase transition is distinctive. The results also suggest potentially therapeutic, anti-trichomonad activity of microtubule inhibitors such as nocodazole. The cultured parasite may prove useful as a model for the mitotic cell cycle in the absence of G1/S phase transitional activities universal in yeasts and vertebrate cells.

Histone H3 Variants in Trichomonas vaginalis

“…In T. vaginalis, immunostaining of TVAG_224460-HA yielded two distinct patterns: (i) TVAG_ 224460-HA was observed as six discrete dots in 20% of examined cells, corresponding to the number of T. vaginalis chromosomes in the G 1 phase (13), or (ii) TVAG_224460-HA appeared as six sets of double dots in about 80% of nuclei. This result is consistent with a duplicated chromatin state and monocentric chromosome appearance during the G 2 phase of the cell cycle, which is a dominant phase in T. vaginalis cultures (10,28). Importantly, single as well as double dots organized at the periphery of the interphase nucleus.…”

Tritrichomonas foetus: induced division synchrony by hydroxyurea

“…Previous studies have shown that even at high concentrations (15 mM) HU did not have a detectable effect on the Trichomonas vaginalis cell cycle (Riley et al 1994). We determined the minimum concentration of HU required for the trichomonads to traverse their cell cycle reaching a blockage point with no apparent toxicity to the majority of cells (Figs.…”

The effect of drugs on cell structure of Tritrichomonas foetus

“…We have found that FCM can reliably detect perturbations to the cell cycle of T. foetus following treatment with drugs. FCM experiments performed by Riley et al (1994) demonstrated the effects of several drugs, including colchicine and nocodazole, in T. vaginalis. Arrest of cells in G2/M phase was also achieved and the phenotype was the same as described above.…”