RESUMO
Aurora kinases possess a conserved catalytic domain (CD) and a N-terminal domain (ND) that varies in size and sequence. We have previously reported that the N-terminal domain of AuroraA (AurA) participates in the localization of the kinase to the centrosome in interphase. AuroraB (AurB) is a chromosome passenger protein and its N-terminal domain is not necessary for its localization or function during mitosis. Using various combinations of GFP-AurA and AurB protein domains we show that AurB N-terminal domain is required for nuclear localization in Xenopus XL2 cells in interphase. In human cells, however, we found both AurA and AurB kinases in the nucleus, AurA being mainly cytoplasmic and AurB mainly nuclear. Both proteins are actively excluded from the nucleus by a CRM1 dependent pathway. Interestingly, at a functional level, in interphase, every combination of Aurora kinase domains (ND-CD) rescues histone H3 Serine10 phosphorylation defect induced by AurB knockdown. This clearly indicates the presence of a functional AurA in the nucleus. However, the chimera ND-AurA/CD-AurB was much more efficient than the ND-AurB/ CD-AurA to rescue multinucleation also induced by AurB knockdown. This indicates that the catalytic domain of AurB is required to fulfill specific functions during mitosis that cannot be fulfilled by the catalytic domain of AurA, probably for localization reasons during mitosis.
Assuntos
Interfase/fisiologia , Proteínas Serina-Treonina Quinases/análise , Animais , Aurora Quinase B , Aurora Quinases , Núcleo Celular/metabolismo , Células Cultivadas , Centrossomo/metabolismo , Proteínas de Fluorescência Verde/genética , Proteínas de Fluorescência Verde/metabolismo , Células HeLa , Humanos , Proteínas Serina-Treonina Quinases/química , Proteínas Serina-Treonina Quinases/metabolismo , Estrutura Terciária de Proteína , Transfecção , XenopusRESUMO
The CDK11 (cyclin-dependent kinase 11) gene has an internal ribosome entry site (IRES), allowing the expression of two protein kinases. The longer 110-kDa isoform is expressed at constant levels during the cell cycle and the shorter 58-kDa isoform is expressed only during G2 and M phases. By means of RNA interference (RNAi), we show that the CDK11 gene is required for mitotic spindle formation. CDK11 RNAi leads to mitotic checkpoint activation. Mitotic cells are arrested with short or monopolar spindles. gamma-Tubulin as well as Plk1 and Aurora A protein kinase levels are greatly reduced at centrosomes, resulting in microtubule nucleation defects. We show that the mitotic CDK11(p58) isoform, but not the CDK11(p110) isoform, associates with mitotic centrosomes and rescues the phenotypes resulting from CDK11 RNAi. This work demonstrates for the first time the role of CDK11(p58) in centrosome maturation and bipolar spindle morphogenesis.
Assuntos
Centrossomo/enzimologia , Centrossomo/fisiologia , Quinases Ciclina-Dependentes/metabolismo , Fuso Acromático/enzimologia , Fuso Acromático/fisiologia , Aurora Quinases , Proteínas de Ciclo Celular/metabolismo , Núcleo Celular/metabolismo , Polaridade Celular , Quinases Ciclina-Dependentes/genética , Células HeLa , Humanos , Microtúbulos/metabolismo , Mitose , Fenótipo , Ligação Proteica , Proteínas Serina-Treonina Quinases/metabolismo , Subunidades Proteicas/genética , Subunidades Proteicas/metabolismo , Proteínas Proto-Oncogênicas/metabolismo , Interferência de RNA , Quinase 1 Polo-LikeRESUMO
As Aurora kinases are overexpressed in a large number of cancers, and ectopic expression of Aurora generates polyploid cells containing multiple centrosomes, it has been tempting to suggest that Aurora overexpression provokes genetic instability underlying the tumorigenesis. However, examination of the evidence suggests a more complex relationship. Overexpression of Aurora-A readily transforms rat-1 and NIH3T3 cells, but not primary cells, whereas overexpression of Aurora-B induces metastasis after implantation of tumors in nude mice. Why do polyploid cells containing abnormal centrosome numbers induced by Aurora not get eliminated at cell-cycle checkpoints? Does this phenotype determine the origin of cancer or does it only promote tumor progression? Would drugs against Aurora family members be of any help for cancer treatment? These and related questions are addressed in this review (which is part of the Chromosome Segregation and Aneuploidy series).
Assuntos
Aneuploidia , Neoplasias/enzimologia , Neoplasias/genética , Proteínas Serina-Treonina Quinases/genética , Proteínas Serina-Treonina Quinases/fisiologia , Animais , Aurora Quinase A , Aurora Quinase B , Aurora Quinases , Ciclo Celular , Centrossomo/enzimologia , Humanos , Masculino , Meiose , Camundongos , Modelos Biológicos , Neoplasias/etiologia , Oncogenes , Ploidias , RatosRESUMO
Protein kinases and phosphatases play crucial roles in all the major cellular processes, such as signal transduction, cell differentiation, cell proliferation and cell cycle progression. Protein phosphorylation or dephosphorylation can form the basis of many critical processes, including enzyme activation or inactivation, protein localization and protein degradation. Given the importance of protein kinases to cellular development and function, it is critical that there are effective ways of disseminating information on protein kinases to the research community. This review describes such a web resource, 'The Protein Kinase Resource' (http://pkr.sdsc.edu/html/index.shtml), which serves as a repository for cellular and molecular data on protein kinases.
