Cycling without cyclins.

Complex oscillations in the activation and inactivation of cyclin-dependent kinase complexes propel mammalian cells through the cycle. A recent spate of studies seems to indicate that many, if not most, of these seemingly essential molecules may, in some senses, be dispensable. If true, that would mean the essential components of the mammalian cell cycle are not much different from those found in prokaryotes. That, in turn, would imply a fair amount redundancy exists in the system which may call into question current cancer treatment strategies designed to target some of these "dispensable" cell cycle control molecules.