title: Ultrasensitivity and positive feedback to promote sharp mitotic entry.
abstract: In this issue, Trunnell et al. (2011) show that in mitotic entry the positive feedback that drives the activation of cyclin-dependent kinase (Cdk) involves a very ultrasensitive step of phosphorylation of Cdc25C by Cdk, thus strongly contributing to the switch-like behavior of this essential cell-cycle transition.
authors.affiliation: Institut de Biologie Moléculaire et Cellulaire, 1 Rue Laurent Fries, 67400 Illkirch Cedex, France.
authors.forename: Youlian
authors.initials: Y
authors.lastname: Goulev
authors.forename: Gilles
authors.initials: G
authors.lastname: Charvin