RESUMEN
Polo-like kinases (Plks) perform crucial functions during mitosis, cytokinesis and centriole duplication. Plk2 is activated in early G1 phase and is involved in the reproduction of centrosomes. However, the mechanisms underlying Plk2-induced centriole duplication are incompletely understood. Here, we show that Plk2 directly targets the F-box protein F-box/WD repeat-containing protein 7 (Fbxw7), which is a regulator of the ubiquitin-mediated degradation of cyclin E. Plk2 phosphorylates Fbxw7 on serine 176 and the two proteins form a complex in vitro and in vivo. Phosphorylation of Fbxw7 by Plk2 induces destabilization of the F-box protein resulting in accumulation of cyclin E and increased potential for centriole reproduction. In addition, loss of Fbxw7 in human cells leads to uncontrolled centriole duplication, highlighting the importance of Fbxw7 regulation by Plk2. These findings define a previously unknown Plk2-dependent pathway involved at the onset of S phase and in centrosome duplication.
Asunto(s)
Proteínas de Ciclo Celular/metabolismo , Centriolos/metabolismo , Proteínas F-Box/metabolismo , Proteínas Serina-Treonina Quinasas/metabolismo , Ubiquitina-Proteína Ligasas/metabolismo , Proteínas de Ciclo Celular/química , Línea Celular , Ciclina E/metabolismo , Proteínas F-Box/química , Proteína 7 que Contiene Repeticiones F-Box-WD , Humanos , Fosforilación , Fosfoserina/metabolismo , Unión Proteica , Proteínas Quinasas/metabolismo , Estabilidad Proteica , Ubiquitina-Proteína Ligasas/química , UbiquitinaciónRESUMEN
Precise positioning of the mitotic spindle determines the correct cell division axis and is crucial for organism development. Spindle positioning is mediated through a cortical machinery by capturing astral microtubules, thereby generating pushing/pulling forces at the cell cortex. However, the molecular link between these two structures remains elusive. Here we describe a previously uncharacterized protein, MISP (C19orf21), as a substrate of Plk1 that is required for correct mitotic spindle positioning. MISP is an actin-associated protein throughout the cell cycle. MISP depletion led to an impaired metaphase-to-anaphase transition, which depended on phosphorylation by Plk1. Loss of MISP induced mitotic defects including spindle misorientation accompanied by shortened astral microtubules. Furthermore, we find that MISP formed a complex with and regulated the cortical distribution of the +TIP binding protein p150(glued), a subunit of the dynein-dynactin complex. We propose that Plk1 phosphorylates MISP, thus stabilizing cortical and astral microtubule attachments required for proper mitotic spindle positioning.
Asunto(s)
Anafase/fisiología , Proteínas de Ciclo Celular/metabolismo , Metafase/fisiología , Proteínas de Microfilamentos/metabolismo , Microtúbulos/metabolismo , Fosfoproteínas/metabolismo , Proteínas Serina-Treonina Quinasas/metabolismo , Proteínas Proto-Oncogénicas/metabolismo , Huso Acromático/metabolismo , Proteínas de Ciclo Celular/genética , Complejo Dinactina , Dineínas/genética , Dineínas/metabolismo , Células HeLa , Humanos , Proteínas de Microfilamentos/genética , Proteínas Asociadas a Microtúbulos/genética , Proteínas Asociadas a Microtúbulos/metabolismo , Microtúbulos/genética , Fosfoproteínas/genética , Fosforilación/fisiología , Proteínas Serina-Treonina Quinasas/genética , Proteínas Proto-Oncogénicas/genética , Huso Acromático/genética , Quinasa Tipo Polo 1RESUMEN
Both gain and loss of function studies have identified the Polo-like kinase Plk4/Sak as a crucial regulator of centriole biogenesis, but the mechanisms governing centrosome duplication are incompletely understood. In this study, we show that the pericentriolar material protein, Cep152, interacts with the distinctive cryptic Polo-box of Plk4 via its N-terminal domain and is required for Plk4-induced centriole overduplication. Reduction of endogenous Cep152 levels results in a failure in centriole duplication, loss of centrioles, and formation of monopolar mitotic spindles. Interfering with Cep152 function prevents recruitment of Plk4 to the centrosome and promotes loss of CPAP, a protein required for the control of centriole length in Plk4-regulated centriole biogenesis. Our results suggest that Cep152 recruits Plk4 and CPAP to the centrosome to ensure a faithful centrosome duplication process.