Jan Michael Peters

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..2009) report that acetylation of cohesin in S phase transiently counteracts an intrinsic "antiestablishment" activity and, thus, enables establishment of sister chromatid cohesion...

..Wapl depletion also increases the residence time of cohesin on chromatin in interphase. Our data indicate that Wapl is required to unlock cohesin from a particular state in which it is stably bound to chromatin...

..This loss is prevented by proteasome inhibitors, implying that it depends on separase activation. Separase may therefore be able to cleave cohesin at centromeres and on chromosome arms...

..The APC is a ubiquitin ligase composed of at least 11 subunits. The interaction of APC2 and APC11 with E2 enzymes is sufficient for ubiquitination reactions, but the functions of most other subunits are unknown...

..In human cells, separase activation also coincides with the cleavage of separase, but it is not known if this reaction activates separase, which protease cleaves separase, and how separase cleavage is regulated...

..In summary, we show that the protease elution protocol increases the recovery from affinity beads and is compatible with quantitative measurements such as the stoichiometry determination of protein complexes...

..The similarity of the phenotype obtained after expression of nonphosphorylatable SA2 in human cells to that seen after the depletion of Plk1 suggests that SA2 is the critical target of Plk1 in the cohesin dissociation pathway...

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..Cohesin phosphorylation depends on Polo-like kinase and reduces the ability of cohesin to bind to chromatin. These results suggest that Polo-like kinase regulates the dissociation of cohesin from chromosomes early in mitosis...

..Centromeric cohesion is one of the hallmarks of mitotic chromosomes. Our results imply that it is not an intrinsically stable property, because it can easily be destroyed by mitotic kinases, which are kept in check by shugoshin...

..Cdk1 and Aurora kinase studies have been facilitated by small-molecule inhibitors, but few if any potent Plk1 inhibitors have been identified...

..Combination of the results of the cellular studies with Scansite motif prediction enabled us to identify 14 sites on six proteins as direct candidate substrates of AURKB or PLK1...

..Plk1 depletion neither prevents APC phosphorylation nor cyclin A destruction in vivo. These observations imply that APC activation is initiated by Cdk1 already in the nuclei of late prophase cells...

..The approaches we describe here are generally applicable to high-throughput follow-up analyses of phenotypic screens in mammalian cells...

..Analysis of amino acid sequence motifs among phosphorylation sites down-regulated under PLK1 inhibition in this data set identified two potential novel variants of the PLK1 consensus motif...

..Our results suggest that substrates are recruited to the APC/C by binding to a bipartite substrate receptor composed of a coactivator protein and Doc1...

..We propose that cohesin functions as a transcriptional insulator, and speculate that subtle deficiencies in this function contribute to 'cohesinopathies' such as Cornelia de Lange syndrome...

..The mechanism we describe here may therefore be widely conserved among different species...

..Our data indicate that Aurora B contributes to chromosome rigidity and segregation by promoting the binding of condensin I to chromatin. We have also addressed how Aurora B might mediate the dissociation of cohesin from chromosome arms...

..Our data imply that APC/C is activated by the association of Cdh1 with Cdc27, which enables APC/C to recognize the D box of substrates via Cdh1's propeller domain...

..H3 phosphorylation by Aurora B is therefore part of a 'methyl/phos switch' mechanism that displaces HP1 and perhaps other proteins from mitotic heterochromatin...

..and Margottin-Goguet et al. in the June issue of Developmental Cell now show that Emi1 degradation in early mitosis is mediated by beta-Trcp1, an adaptor protein that recruits proteins to the SCF ubiquitin ligase...

..The Mad2 protein is required to delay sister chromatid separation until all chromosomes have been aligned on the mitotic spindle. Two recent studies provide new insights into how Mad2 contributes to this remarkable task...

..Our data indicate that sororin interacts with chromatin-bound cohesin and functions during the establishment or maintenance of cohesion in S or G2 phase, respectively...

..Separase depletion in bone marrow causes aplasia and the presumed death of hematopoietic cells other than erythrocytes. Destruction of sister chromatid cohesion by Separase may be a universal feature of mitosis in eukaryotic cells...

..Mad2 and p31(comet) are components of the spindle assembly checkpoint which controls the fidelity of chromosome segregation. Two recent structural studies reveal new insight into how these proteins achieve this difficult task...

..Our data indicate that the Suv39h-HP1 pathway is not essential for enrichment and mitotic protection of cohesin at centromeres in mammalian cells...

..These observations clarify the structural basis for the inhibition of APC/C by spindle checkpoint proteins...

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..We propose that late mitotic Plk1 activity promotes recruitment of Ect2 to the central spindle, triggering the initiation of cytokinesis and contributing to cleavage plane specification in human cells...

..Here we review what is known about the roles of cohesin and CTCF in regulating gene expression in mammalian cells, and we discuss how cohesin might mediate the insulator function of CTCF...

..5-MDa complex. Recent discoveries have revealed an unexpected multitude of mechanisms that control APC/C activity, and have provided a first insight into how this unusual ubiquitin ligase recognizes its substrates...

..These agents also improve the binding of phosphorylated peptides and block the binding of non-phosphorylated ones. This enrichment procedure takes 30 min, followed by a 100-min HPLC program, including washing and an elution gradient...

..In this article, we discuss the implications of these findings on our current understanding of APC activation...

..We propose that accumulation of cohesin at DNA break sites is not only needed to mediate DNA repair, but also facilitates the recruitment of checkpoint proteins, which activate the intra-S and G2/M checkpoints...