THE ROLE OF CALMODULIN IN KARYOKINESIS AND IN CYTOKINESIS.
| Authors | |
|---|---|
| Year of publication | 2004 |
| Type | Article in Proceedings |
| Conference | 32nd Intarnational Conference on yeasts. |
| MU Faculty or unit | |
| Citation | |
| Field | Genetics and molecular biology |
| Keywords | calmodulin; karyokinesis; cytokinesis; yeasts; yeast cell cycle; cytoskeleton; mutants; indirect immunofluorescence |
| Description | Recently, the intracellular localization of protein calmodulin and cytoskeletal actin in cells of yeast strain Yarrowia lipolytica has been studied by indirect immunofluorescence using anti calmodulin antibody and rhodamine conjugated phalloidin. We have found that there exist relationships between cytoskeletal components and protein calmodulin. Microtubule disassembly is promoted by calmodulin in the presence of Ca2+. Calmodulin is also implicated in regulation of microfilaments. Distributions of calmodulin changes in a typical way during the cell cycle. In the unbudded cell calmodulin localizes to a sharp crescent shaped patch on the cortex of the cell. At bud emergence, calmodulin concentrates to the budding portion. All budded cells exhibit bright staining calmodulin dots at the tip of the bud. In small budded cells are staining dots localized at the bud neck, in cells with large buds calmodulin diffuses throughout the entire bud. At cytokinesis, calmodulin is mainly present at the connecting passage between the mother and daughter cells. Double staining experiments were carried out. They have shown that the location of calmodulin dots coincides with that of actin structures. Calmodulin emerges in mentioned parts of the cell always sooner than actin. This fact proved that calmodulin is required for distribution of actin dots. The finding that calmodulin is unconditionally needed for nuclear division was particularly important. Therefore we studied new, intentionally prepared mutants Y. lipolytica in our present experiments. We found that opened cell cycle without sufficient level of calmodulin stops in M-phase. Inhibition of karyokinesis start caused by the low level of calmodulin is reversible and without consequences, if the blockade takes less than four hours. After increase in calmodulin level, the karyokinesis starts in 15 minutes and it passes correctly. But if the blockade of karyokinesis takes more than four hours as a result of extremely low level of intracellular calmodulin, the cell reacts to calmodulin level normalization late (after 4 hours) and the process of the karyokinesis is very aberrant. However, the cytokinesis is not restored no more. After about 20 hours, we can observe cell formations vary in size in the culture with from two to four nuclei different in size and DNA content. In these cells calmodulin and actin dots are dispersed all over the periphery of cell and their number and size are strongly reduced. |
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