title: Cyclin I is involved in the regulation of cell cycle progression.
abstract: Cyclins control cell cycle progression by regulating the activity of cyclin-dependent kinases (Cdks). Cyclin I is a member of the cyclin family because of the presence of a cyclin box motif. It has been suggested that Cyclin I is involved in various biological processes, such as cell survival, angiogenesis, and cell differentiation. However, whether or not Cyclin I has a role in regulating the cell cycle similarly to other cyclins has yet to be clarified. Therefore, we investigated the role for Cyclin I in cell cycle progression. We showed that the protein level of Cyclin I oscillated during the cell cycle, and that Cyclin I was subjected to ubiquitination and degradation in cells. The interaction between Cyclin I and Cdk5 was detected in cells overexpressed with both proteins. Furthermore, depletion of Cyclin I by siRNAs prevented cell proliferation, suggesting the positive role of Cyclin I for the cell cycle progression. In addition, flow cytometric analysis revealed that cells depleted of Cyclin I were accumulated at G₂/M phases. By using HeLa.S-Fucci (fluorescent ubiquitination-based cell cycle indicator) cells, we further confirmed that knockdown of Cyclin I induced cell cycle arrest at S/G₂/M phases. These results strongly suggest that Cyclin I has the role in the regulation of cell cycle progression.
authors.affiliation: Biosignal Research Center, Kobe University, Kobe, Japan.
authors.forename: Taiki
authors.initials: T
authors.lastname: Nagano
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Hashimoto
authors.forename: Akio
authors.initials: A
authors.lastname: Nakashima
authors.forename: Shin-ichi
authors.initials: S
authors.lastname: Hisanaga
authors.forename: Ushio
authors.initials: U
authors.lastname: Kikkawa
authors.forename: Shinji
authors.initials: S
authors.lastname: Kamada
mesh_terms: D002453:Cell Cycle / Q000502:physiology*; D049109:Cell Proliferation; D056749:Cyclin I / Q000235:genetics / Q000378:metabolism*; D051360:Cyclin-Dependent Kinase 5 / Q000378:metabolism; D018844:Cyclin-Dependent Kinases / Q000378:metabolism*; D005434:Flow Cytometry; D005453:Fluorescence; D055785:Gene Knockdown Techniques; D006367:HeLa Cells; D006801:Humans; D059748:Proteolysis; D054875:Ubiquitination
chemical_list: D056749:Cyclin I; D051360:Cyclin-Dependent Kinase 5; D018844:Cyclin-Dependent Kinases
keywords: Cdk5; Fucci; cell proliferation; cyclin I; ubiquitination
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