Effects of rok1 gene deletion on mitosis in fission yeast at appropriate and stressful temperatures and the molecular mechanisms

The rok1 gene encodes the ATP‑dependent RNA helicase Rok1, which is involved in regulating the maturation of small subunit ribosomal RNA and thus ribosome biogenesis. However, the regulation of cellular mitotic dynamics by the rok1 gene deletion is currently unclear. In the present study, fluorescent protein labeling and live cell imaging techniques were used to investigate the effects of rok1 deletion on the dynamics of microtubules, actin and kinetochores during mitosis at 25 and 37˚C, and RNA‑sequencing and bioinformatics analyses were used to reveal the key genes. Analysis of the live cell imaging results revealed that, in mitosis, the initiation length and contraction length of actin rings were both shortened and the contraction rate was decreased at 25 and 37˚C. The separation process of kinetochores was inhibited at 25 and 37˚C, and the inhibition was more severe at the higher temperature of 37˚C. Analysis of RNA sequencing results showed that upregulation of myo51 and blt1 resulted in delayed actin ring assembly and slowed actin ring contraction in the rok1Δ strain. In addition, psm1 and psc3 were upregulated and are key genes affecting the ability of kinetochores to move on the spindle and the cohesion of sister chromatids. The present study revealed that the Rok1 protein not only influences the actin polymerization process, participate in the regulation of actin ring assembly and contraction, and cytoplasmic division, but also affects the migration ability of kinetochores on the spindle and participate in the regulation of the formation and maintenance of cohesion between sister chromatids, which provides a certain scientific basis for further exploring the function of the Rok1 protein in cell division.