Trichomonas vaginalis is an early divergent protozoan parasite that causes trichomoniasis, the most common non-viral sexually transmitted infection. In metazoans, there is abundant and detailed research on the cell cycle and the components involved in the regulation mechanisms. Regulators such as the cyclin-dependent kinases (CDKs) and cyclins activate the highly regulated processes of cell division. While CDKs have important roles in the phosphorylation of specific substrates, cyclins are important activating-components of CDKs that allow orderly passage through the different stages of the cell cycle. Cell cycle cyclins are characterized by showing drastic changes in their concentration during the cell cycle progression. However, in protists such as T. vaginalis, some biological processes such as cell cycle regulation remain less well studied. In an attempt to gain insight into cell cycle regulation in T. vaginalis, as an initial approach we characterized four proteins with features of cyclins. The genes encoding these putative cyclins were cloned to produce the recombinant proteins TvCYC1, TvCYC2, TvCYC3, and TvCYC4. The functional activity of TvCYC2, TvCYC3, and TvCYC4 was assessed through their complementation of a yeast cln1,2,3Δ mutant strain; TvCYC1 was not able to complement this mutant. Furthermore, our results suggest that TvCYC1, TvCYC2, and TvCYC3, are able to interact with and activate the kinase activity of TvCRK1, a kinase previously characterized by our group. The present study represents the first characterization of cyclins potentially involved in cell cycle regulation in T. vaginalis.

阴道毛滴虫是一种早期分化的原生动物寄生虫，可引起毛滴虫病，这是最常见的非病毒性传播感染。在后生动物中，对细胞周期和参与调控机制的成分进行了丰富而详尽的研究。细胞周期蛋白依赖性激酶 (CDK) 和细胞周期蛋白等调节剂可激活高度调节的细胞分裂过程。虽然 CDK 在特定底物的磷酸化中具有重要作用，但细胞周期蛋白是 CDK 的重要激活成分，它允许有序地通过细胞周期的不同阶段。细胞周期细胞周期蛋白的特点是在细胞周期进程中其浓度会发生剧烈变化。然而，在T. vaginalis等原生生物中, 一些生物过程如细胞周期调节仍然没有得到很好的研究。为了深入了解T. vaginalis中的细胞周期调节，作为初始方法，我们对四种具有细胞周期蛋白特征的蛋白质进行了表征。编码这些假定细胞周期蛋白的基因被克隆以产生重组蛋白 TvCYC1、TvCYC2、TvCYC3 和 TvCYC4。TvCYC2、TvCYC3 和 TvCYC4 的功能活性是通过它们与酵母cln1、2、3的互补来评估的Δ突变株；TvCYC1 不能补充这个突变体。此外，我们的结果表明 TvCYC1、TvCYC2 和 TvCYC3 能够与 TvCRK1 相互作用并激活其激酶活性，TvCRK1 是我们小组之前表征的一种激酶。本研究代表了可能参与T. vaginalis细胞周期调节的细胞周期蛋白的第一个特征。