Analysis Of Metaphase II-Anaphase II Transition

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(2) Metaphase II-Anaphase II transition (resumption of the second meiosis)
During resumption period of cell cycle, sister chromatids pass anaphase/telophase transition and completed meiosis II by extrusion of the second polar body. After that, chromatin decondensation and the pronuclei formation are occurred. In this stage, the important proteins are involved in resumption of meiosis II composed of G-protein, CaM kinase II, APC/C and separase.
Guanine nucleotide-binding regulatory proteins (G-proteins) are a family of proteins that is related to transmitting chemical signals outside the cell cause of intracellular changes. G-proteins can be activated by G-protein couple receptor, transmembrane receptor. The results of mRNA encoding
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Before fertilization, mammalian oocytes are arrested in M II by an activity of cytostatic factor (CSF). APC/C is inhibited by CSF to prevent metaphase-anaphase transition and complete of meiosis II. Cyclin B and CDK2 control the establishment of CSF and Mos signaling pathway and also involve in controlling activity of CSF. The activation of APC/C at metaphase targets destruction-box containing substrates, such as degradation of securin and cyclin B1, to complete meiosis II division.
Separase is a cysteine protease. It is responsible to stimulate anaphase in meiosis II by hydrolyzing cohesion the protein that responsible for binding sister chromatids during metaphase. Securin/separase/cohesion pathway regulates chromosome segregation during meiotic metaphase- to- anaphase transition in meiosis II. Separase activation requires before securin degradation, its associated inhibitor. After degradation of securin, Separase activation cleaves the cohesins and followed by separation of chromatid and initiation of anaphase stage (Terret et al. 2003).
In the summary of meiosis II resumption, After sperm fusion, G protein induces the increasing of Ca2+ to stimulate calmodulin-dependent protein kinase II (Cam kinase II). After that, CaM kinase II inhibits the activation of Emi and then APC/C is activated by association with cdc20 lead to cyclin B1 and securin degradation. After
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