PDF Distinct mechanisms of cell cycle arrest control the decision Biology Diagrams Almost 30 years ago, cytostatic factor (CSF) was identified as the activity responsible for the MII arrest, yet today its molecular make-up remains mysterious. Ten years ago, both Mos, a MAP kinase kinase kinase, and MAP kinase were shown to be capable of blocking a one-cell embryo in metaphase, and subsequent work has shown that they are In most vertebrates, oocytes await fertilization while arrested at metaphase of meiosis II. This resting state can be stable for many hours and depends on a cytoplasmic activity termed cytostatic factor (CSF). Recently, members of the novel Emi/Erp family of proteins have been put forward as important components of CSF. Mad1 and Mad2 arrest cleaving Xenopus embryos in metaphase. Mad1 and Mad2 proteins are present in the early embryo even though nocodazole does not affect cell cycle progression until the gastrula stage (Minshull et al., 1994; Clute and Masui, 1995).However, if CSF components are introduced into cells of the embryo, the cell cycle arrests in metaphase of the next mitosis (Masui and Markert
It is shown that the zinc fluxes work, in part, by altering the activity of the cytostatic factor (CSF), the cellular activity required for the establishment and maintenance of metaphase II arrest in the mature, unfertilized egg, which supports the conclusion that zinc itself, through its interaction with EMI2, is a central component of the CSF.
Arrested! CSF stops the cycle: Trends in Cell Biology Biology Diagrams
The second causes cell cycle arrest when injected into a mitotically dividing embryo, leading to its designation as cytostatic factor (CSF) (see Fig. 1). This arrest is characterized by the presence of a metaphase spindle and high Cdk1 activity in the injected cell, just like the physiological CSF arrest that occurs in meiosis II. To await fertilization, oocytes have to maintain a cell cycle arrestalso named cytostatic factor or CSF arrest (Schmidt et al, 2006)-for an extended time in metaphase II. Sgo2 localized by Mps1 Oocytes from higher chordates, including man and nearly all mammals, arrest at metaphase of the second meiotic division before fertilization. This arrest is due to an activity that has been termed 'Cytostatic Factor'. Cytostatic Factor maintains arrest through preventing loss in Maturation-Promoting Factor (MPF; CDK1/cyclin B). Physiologically, Cytostatic Factor - induced metaphase arrest is
However, if CSF components are introduced into cells of the embryo, the cell cycle arrests in metaphase of the next mitosis (Masui and Markert, 1971; for review see Tunquist and Maller, 2003). To determine whether Mad1 and Mad2 possess CSF activity, we injected recombinant forms of each protein into blastomeres of two-cell stage Xenopus embryos
