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<p>CSV import</p> <p><b>New page</b></p><div>[[Image:Cyclin Expression.svg|thumb|422px]] &#039;&#039;&#039;Cyclin B&#039;&#039;&#039; is a type of [[cyclin]] protein that plays a crucial role in the [[cell cycle]], particularly in the transition from [[G2 phase]] to [[mitosis]] in the [[eukaryotic cells]]. Cyclin B, along with its [[cyclin-dependent kinase]] (CDK), CDK1 (also known as CDC2), forms the maturation-promoting factor (MPF), which is essential for a cell to proceed from the G2 phase to mitosis. This article provides an overview of the structure, function, regulation, and importance of Cyclin B in cell cycle control.<br /> <br /> ==Structure==<br /> Cyclin B is characterized by its periodic accumulation and degradation during the cell cycle. Its levels begin to rise in the S phase, peak in the G2 phase, and rapidly degrade during the mitosis phase. The structure of Cyclin B includes a cyclin box, which is a conserved domain necessary for binding to CDK1, and a destruction box, which targets the protein for degradation via the [[ubiquitin-proteasome pathway]].<br /> <br /> ==Function==<br /> The primary function of Cyclin B is to activate CDK1, forming the MPF complex. This activation leads to the initiation of mitosis, where the cell undergoes division to produce two daughter cells. The Cyclin B-CDK1 complex phosphorylates various substrates involved in chromosome condensation, nuclear envelope breakdown, and the formation of the [[mitotic spindle]], thereby driving the cell into mitosis.<br /> <br /> ==Regulation==<br /> The activity and levels of Cyclin B are tightly regulated throughout the cell cycle. Cyclin B synthesis begins in the S phase and accumulates during the G2 phase. The regulation of Cyclin B involves both transcriptional controls and post-translational modifications. Phosphorylation of Cyclin B-CDK1 complex by [[Wee1 kinase]] inhibits its activity, while dephosphorylation by [[Cdc25 phosphatase]] activates it. The timely degradation of Cyclin B through the ubiquitin-proteasome pathway is crucial for the exit from mitosis and the progression of the cell cycle.<br /> <br /> ==Importance==<br /> Cyclin B is essential for the proper timing and regulation of mitosis. Aberrations in Cyclin B levels or regulation can lead to improper cell division, which may contribute to the development of [[cancer]] and other diseases. As such, Cyclin B and its regulatory mechanisms are of significant interest in cancer research, with potential implications for the development of therapeutic interventions targeting cell cycle control.<br /> <br /> ==See Also==<br /> * [[Cyclin]]<br /> * [[Cell cycle]]<br /> * [[Mitosis]]<br /> * [[Cyclin-dependent kinase]]<br /> * [[Ubiquitin-proteasome pathway]]<br /> <br /> [[Category:Cell cycle]]<br /> [[Category:Proteins]]<br /> {{Cell-biology-stub}}</div>

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