Sister chromatid separation in vivo and in vitro.

The proteins that are involved in the mechanics of sister chromatid separation and that regulate this process are (as yet) largely unknown. Topoisomerase II activity is known to be essential for sister chromatid separation, probably to decatenate sister chromatids that have remained linked until the metaphase/anaphase transition, but other unidentified proteins are also required. An in vitro sister chromatid separation assay has been developed recently that complements the previously existing techniques used to study the process. This assay had led to some new insights into sister chromatid separation, showing, for example, that the process is regulated by ubiquitin-mediated proteolysis of protein(s) that are not known mitotic cyclins.