| Research Abstract |
To elucidate the molecular mechanisms of cell division in animal cells,by using Tetrahymena's cell-division-arrest mutants, cdaA and cdaC, we have analyzed mechanisms for division plane determination, division furrow formation, furrowing, contraction-related contractle ring microfilament disassembly, and for calcium-regulation of division furrow constriction.
Concerning division plane determination, it was evident that cdaA mutant gene product,p85, plaied a crucial role in the determination and it served as polymerization nuclei of the contractile ring actin filaments. As for division furrow constriction, by the analysis of cdaC mutant, the mutant gene product is considered to be an actin-binding protein capable of bundling the contractile ring microfilaments. We recently found a protein which associates with Tetrahymena's 14-nm filaments and we identified it as EF-1alpha from its gene analysis. We are now investigating the relation between EF-1alpha and cdaC gene product, since Tetrahymena EF-1alpha has an actin-bundling activity. In cytokinesis, it has been proposed that contractile ring microfilament disassembly occurs accompanying with the contraction of contractile ring. In this regard, we found that an actin-polymerization-inhibitory factor, profilin of Tetrahymena, colocalized with actin filaments in the division furrow, suggesting the involvement of profilin in the formation and disassembly of contractile ring microfilaments. Concerning the calcium-regulation of division furrow constriction, we cloned the genes for 3 kinds of calcium-binding proteins (calmodulin, TCBP-23, and TCBP-25) from Tetrahymena. We are now scrutinized their biological functions in cytokinesis by injecting the gene or modified gene products yielded in E. coli.
|
