The mechanism regulating the dissociation of the centrosomal protein C-Nap1 from mitotic spindle poles

The centrosomal protein C-Nap1 is thought to play an important role in centrosome cohesion during interphase of the cell cycle. At the onset of mitosis, when centrosomes separate for bipolar spindle formation, C-Nap1 dissociates from centrosomes. Here we report the results of experiments aimed at determining whether the dissociation of C-Nap1 from mitotic centrosomes is triggered by proteolysis or phosphorylation. Specifically, we analyzed both the cell cycle regulation of endogenous C-Nap1 and the fate of exogenously expressed full-length C-Nap1. Western blot analyses suggested a reduction in the endogenous C-Nap1 level during M phase, but studies using proteasome inhibitors and destruction assays performed in Xenopus extracts argue against ubiquitin-dependent degradation of C-Nap1. Instead, our data indicate that the mitotic C-Nap1 signal is reduced as a consequence of M-phase-specific phosphorylation. Overexpression of full-length C-Nap1 in human U2OS cells caused the formation of large structures that embedded the centrosome and impaired its microtubule nucleation activity. Remarkably, however, these centrosome-associated structures did not interfere with cell division. Instead, centrosomes were found to separate from these structures at the onset of mitosis, indicating that a localized and cell-cycle-regulated activity can dissociate C-Nap1 from centrosomes. A prime candidate for this activity is the centrosomal protein kinase Nek2, as the formation of large C-Nap1 structures was substantially reduced upon co-expression of active Nek2. We conclude that the dissociation of C-Nap1 from mitotic centrosomes is regulated by localized phosphorylation rather than generalized proteolysis

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Division of Labour and Self-Reported Mental Requirements in Human Services: Retail Sale Jobs

Significant associations between self-reported “whole units” of work and self-reported mental task requirements as well as personal outcomes are well known. Also of interest is, however, whether a significant association also exists between the underlying objective assignment of tasks, i.e. the division of labour, and self-reported mental requirements. Such an association would represent a concrete starting point for job design or redesign. We analyzed this question for retail sale jobs as an example of the numerous human service jobs, which usually consist of customer- and object-centred tasks. The study (N = 558 employees) evaluated the potential association between documented assignments of customer-centred and goods-centred activities and employees’ perceived mental requirements, skill utilisation, and learning on the job, as well as mental difficulties. A significant association of moderate effect size between the objective division of labour and self-reported mental job requirements was shown. Theoretical and practical consequences of this association are also discussed

Verhältnis- und verhaltenspräventives Gestalten dialogisch-interaktiver Erwerbsarbeit

Der Beitrag skizziert die Anforderungsbesonderheiten von dialogisch-interaktiver Erwerbsarbeit, d. h. von klientenverändernden, klientenbeeinflussenden und klientenbezogenen Arbeitstätigkeiten. Möglichkeiten zum verhältnis- und verhaltenspräventiven Gestalten von Interaktionsarbeit im Dienstleistungsbereich werden skizziert. Hierzu werden Beispiele aus der Kranken- und Seniorenpflege, der Bildung sowie dem Einzel- und Großhandel referiert. Die dargestellten Beispiele zeigen Möglichkeiten der Verhältnisprävention (Primat der Verhältnisgestaltung) bei dialogisch-interaktiver Dienstleistungsarbeit. Die Bedeutung der Integration der Befähigung zu präventiver Arbeitsgestaltung in die berufliche Aus- und Weiterbildung wird betont.Praktische Relevanz Arbeitsgestaltung mit dem Ziel der Verhütung von Gefährdungen ist auch in Humandienstleistungstätigkeiten unerlässlich. Für die hohe Zahl der Beschäftigten, die betreuende, ausbildende, pflegerische, therapeutische oder beratende/verkaufende Tätigkeiten ausüben, ist eine präventive Gestaltung der Arbeit erforderlich, um Fehlbeanspruchungen zu vermeiden. Die Arbeit kann sowohl verhältnis-(bedingungs-) als auch verhaltensbezogen präventiv gestaltet werden, wobei der Verhältnisprävention der Vorrang zu geben ist. Der Beitrag führt Beispiele aus der verhältnis- und verhaltensbezogenen Prävention an und benennt dafür nutzbare Verfahren und Vorgehensweisen

The mechanism regulating the dissociation of the centrosomal protein C-Nap1 from mitotic spindle poles

The centrosomal protein C-Nap1 is thought to play an important role in centrosome cohesion during interphase of the cell cycle. At the onset of mitosis, when centrosomes separate for bipolar spindle formation, C-Nap1 dissociates from centrosomes. Here we report the results of experiments aimed at determining whether the dissociation of C-Nap1 from mitotic centrosomes is triggered by proteolysis or phosphorylation. Specifically, we analyzed both the cell cycle regulation of endogenous C-Nap1 and the fate of exogenously expressed full-length C-Nap1. Western blot analyses suggested a reduction in the endogenous C-Nap1 level during M phase, but studies using proteasome inhibitors and destruction assays performed in Xenopus extracts argue against ubiquitin-dependent degradation of C-Nap1. Instead, our data indicate that the mitotic C-Nap1 signal is reduced as a consequence of M-phase-specific phosphorylation. Overexpression of full-length C-Nap1 in human U2OS cells caused the formation of large structures that embedded the centrosome and impaired its microtubule nucleation activity. Remarkably, however, these centrosome-associated structures did not interfere with cell division. Instead, centrosomes were found to separate from these structures at the onset of mitosis, indicating that a localized and cell-cycle-regulated activity can dissociate C-Nap1 from centrosomes. A prime candidate for this activity is the centrosomal protein kinase Nek2, as the formation of large C-Nap1 structures was substantially reduced upon co-expression of active Nek2. We conclude that the dissociation of C-Nap1 from mitotic centrosomes is regulated by localized phosphorylation rather than generalized proteolysis

Direct Bonds Between Metal Atoms: Zn, Cd, and Hg Compounds with Metal–Metal Bonds

11 páginas, figurasThe synthesis and characterization of [Zn2(η5-C5Me5)2], a stable molecular compound with a Zn-Zn bond and the first example of a dimetallocene structure, has opened a new chapter in the organometallic chemistry of zinc and in metallocene chemistry. The existence of two directly bonded zinc atoms demonstrates that the [Zn-Zn]2+ unit, the lightest Group 12 homologue of the well-known [Hg-Hg]2+ ion, can be stabilized by appropriate ligands. Activity in this area has increased enormously in the few years since the determination of the structure of this molecule. Numerous theoretical studies have been devoted to the investigation of the electronic, structural, and spectroscopic properties of this and related compounds, and new metal–metal coordination and organometallic compounds of zinc, cadmium, and mercury have been synthesized and structurally characterized. This Minireview gives an overview of activity in this field during the past three to four years.Peer reviewe