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Myosin II regulatory light chains have an important role in the organization and function of the contractile machinery at cytokinesis. Two recent reports provide new insights into these important proteins.
Loss of sister-chromatid cohesion triggers chromosome segregation. Several recent reports show that the protease Esp1 cleaves the cohesin subunit Scc1/Mcd1 to induce sister-chromatid segregation in yeast and vertebrates. This finding indicates that cohesin cleavage may control sister-chromatid separation in all eukaryotes.
Recent work has revealed an evolutionarily conserved trio of proteins that regulate cell polarity in epithelial cells, embryonic blastomeres and neural precursors. This common cell-polarity mechanism is used in cell-specific ways, as highlighted by the recent finding that at least two different types of asymmetric division are observed in Drosophila neural precursors.
The process of cell division, or mitosis, has fascinated biologists since its discovery in the late 1870s. Progress through mitosis is traditionally divided into stages that were defined over 100 years ago from analyses of fixed material from higher plants and animals. However, this terminology often leads to ambiguity, especially when comparing different systems. We therefore suggest that mitosis can be re-staged to reflect more accurately the molecular pathways that underlie key transitions.
