Proteolytic destruction of cyclins is a fundamental process for cell
division. At the end of mitosis, degradation of mitotic cyclins results in
the inactivation of cyclin-dependent kinases. Cyclin proteolysis is
triggered by the anaphase-promoting complex/cyclosome (APC/C), a
multi-subunit complex which contains ubiquitin ligase activity. Recent data
in yeast demonstrated that a partial degradation of the mitotic cyclin
Clb2, mediated by APC/C and its activator protein Cdc20, is essential and
sufficient for the mitotic exit. Remarkably, a complete inactivation of
cyclin-dependent kinases seems to be not essential. This review discusses
recent novel insights into cyclin destruction and its implications for the
mitotic exit.