RESUMO
p31(Comet) is a well-known interacting partner of the spindle assembly checkpoint (SAC) effector molecule Mad2. At the molecular level it is well established that p31(Comet) promotes efficient mitotic exit, specifically the metaphase-anaphase transition, by antagonizing Mad2 function. However, there is little knowledge of how p31(Comet) is regulated or the physiological importance of controlling p31(Comet). Here, we show that the Rb-E2F pathway regulates p31(Comet) expression. In multiple tumor types (including breast and lung) p31(Comet) expression is increased along with Mad2. Expression of this antagonist-target pair is coordinated in cells and correlated in cancer. Moreover, a narrow range of p31(Comet):Mad2 ratios is compatible with cellular viability. Our data suggest that coordinate regulation is important for the outgrowth of oncogenic cell populations. Our findings suggest that altered p31(Comet):Mad2 expression ratios may provide new insight into altered SAC function and the generation of chromosomal instability in tumors.
Assuntos
Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Proteínas de Ciclo Celular/metabolismo , Proteínas Mad2/metabolismo , Proteínas Nucleares/metabolismo , Proteínas Adaptadoras de Transdução de Sinal/genética , Animais , Ciclo Celular , Proteínas de Ciclo Celular/genética , Linhagem Celular , Proliferação de Células , Fatores de Transcrição E2F/metabolismo , Regulação da Expressão Gênica , Humanos , Proteínas Mad2/genética , Camundongos , Neoplasias/metabolismo , Proteínas Nucleares/genética , Proteína do Retinoblastoma/genética , Proteína do Retinoblastoma/metabolismo , Fuso Acromático/metabolismoRESUMO
Rb/E2F regulates many genes that encode proteins required for the cell cycle. Using affymetrix microarrays we previously identified genes regulated by the Rb proteins p130 and p107, many of which are involved in the cell cycle. Several genes with unknown functions were also repressed by p130 and p107, of which some have recently been found to have various roles in mitosis, the spindle checkpoint and cytokinesis. This study focuses on the regulation of borealin/dasra/cdca8, which encodes a recently discovered member of the chromosomal passenger complex. It is recorded that borealin is a cell cycle regulator, down-regulated in response to p53/Rb-signaling, and up-regulated in many types of cancerous tissues.
Assuntos
Proteínas de Ciclo Celular/metabolismo , Regulação da Expressão Gênica/fisiologia , Genes p53/fisiologia , Neoplasias/genética , Proteína do Retinoblastoma/metabolismo , Transdução de Sinais/fisiologia , Proteína Supressora de Tumor p53/metabolismo , Processamento Alternativo/genética , Biomarcadores Tumorais/metabolismo , Ciclo Celular , Proteínas de Ciclo Celular/genética , Divisão Celular/genética , Fatores de Transcrição E2F/genética , Fatores de Transcrição E2F/metabolismo , Inativação Gênica , Células HCT116 , Humanos , Neoplasias/metabolismo , Proteína do Retinoblastoma/genética , Proteína p107 Retinoblastoma-Like/genética , Proteína p107 Retinoblastoma-Like/metabolismo , Proteína p130 Retinoblastoma-Like/genética , Proteína p130 Retinoblastoma-Like/metabolismo , Transcrição Gênica , Proteína Supressora de Tumor p53/genéticaRESUMO
BACKGROUND: The main role of the chromosomal passenger complex is to ensure that Aurora B kinase is properly localized and activated before and during mitosis. Borealin, a member of the chromosomal passenger complex, shows increased expression during G2/M phases and is involved in targeting the complex to the centromere and the spindle midzone, where it ensures proper chromosome segregation and cytokinesis. Borealin has a consensus CDK1 phosphorylation site, threonine 106 and can be phosphorylated by Aurora B Kinase at serine 165 in vitro. RESULTS: Here, we show that Borealin is phosphorylated during mitosis in human cells. Dephosphorylation of Borealin occurs as cells exit mitosis. The phosphorylated form of Borealin is found in an INCENP-containing complex in mitosis. INCENP-containing complexes from cells in S phase are enriched in the phosphorylated form suggesting that phosphorylation may encourage entry of Borealin into the chromosomal passenger complex. Although Aurora B Kinase is found in complexes that contain Borealin, it is not required for the mitotic phosphorylation of Borealin. Mutation of T106 or S165 of Borealin to alanine does not alter the electrophoretic mobility shift of Borealin. Experiments with cyclohexamide and the phosphatase inhibitor sodium fluoride suggest that Borealin is phosphorylated by a protein kinase that can be active in interphase and mitosis and that the phosphorylation may be regulated by a short-lived phosphatase that is active in interphase but not mitosis. CONCLUSION: Borealin is phosphorylated during mitosis. Neither residue S165, T106 nor phosphorylation of Borealin by Aurora B Kinase is required to generate the mitotic, shifted form of Borealin. Suppression of phosphorylation during interphase is ensured by a labile protein, possibly a cell cycle regulated phosphatase.