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Query: UMLS:C0033036 (APC)
 10,214 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Cdc20 is a substrate adaptor and activator of the anaphase-promoting complex/cyclosome (APC/C), the E3 ubiquitin ligase whose activity is required for anaphase onset and exit from mitosis. A green fluorescent protein derivative, Cdc20-GFP, bound to centrosomes throughout the cell cycle and to kinetochores from late prophase to late telophase. We mapped distinct domains of Cdc20 that are required for association with kinetochores and centrosomes. FRAP measurements revealed extremely rapid dynamics at the kinetochores (t1/2 = 5.1 s) and spindle poles (t1/2 = 4.7 s). This rapid turnover is independent of microtubules. Rapid transit of Cdc20 through kinetochores may ensure that spindle checkpoint signaling at unattached/relaxed kinetochores can continuously inhibit APC/CCdc20 targeting of anaphase inhibitors (securins) throughout the cell until all the chromosomes are properly attached to the mitotic spindle.
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PMID:Rapid microtubule-independent dynamics of Cdc20 at kinetochores and centrosomes in mammalian cells. 1219 7

Cdh1p is a substrate-specific subunit of the anaphase-promoting complex (APC/C), which functions as an E3 ubiquitin ligase to degrade the mitotic cyclin Clb2p and other substrates during the G(1) phase of the cell cycle. Cdh1p is phosphorylated and thereby inactivated at the G(1)/S transition predominantly by Cdc28p-Clb5p. Here we show that Cdh1p is nuclear during the G(1) phase of the cell cycle, but redistributes to the cytoplasm between S phase and the end of mitosis. Nuclear export of Cdh1p is regulated by phosphorylation and requires active Cdc28p kinase. Cdh1p binds to the importin Pse1p and the exportin Msn5p, which is necessary and sufficient to promote efficient export of Cdh1p in vivo. Although msn5delta cells are viable, they are sensitive to Cdh1p overexpression. Likewise, a mutant form of Cdh1p, which is constitutively nuclear, prevents accumulation of Clb2p and leads to cell cycle arrest when overexpressed in wild-type cells. Taken together, these results suggest that phosphorylation-dependent nuclear export of Cdh1p by Msn5p contributes to efficient inactivation of APC/C(Cdh1).
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PMID:Cell cycle-dependent nuclear export of Cdh1p may contribute to the inactivation of APC/C(Cdh1). 1245 58

The Anaphase Promoting Complex/Cyclosome (APC/C) is an E3 ubiquitin ligase that covalently attaches ubiquitins onto proteins to target them for proteolysis by the 26S proteasome. During mitosis, the APC/C is instrumental in allowing the cell to enter and exit from mitosis. The APC/C accomplishes this by using different specificity factors to recognize, interact with, and ubiquitylate key proteins that block cell cycle progression. The specificity factors, Cdc20p and Cdh1p, are not always associated with the APC/C and indeed they have the ability to interact with substrates in isolation. The molecular events that take place in order for Cdc20p and Cdh1p to couple substrates and APC/C are currently being resolved. Meanwhile, evidence has emerged suggesting that at least one of the specificity factors, Cdc20p, might be capable of functioning independently of the APC/C.
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PMID:Cdc20 in S-phase: the Banquo at replication's banquet. 1472 78

The anaphase-promoting complex/cyclosome (APC/C) is an E3 ubiquitin ligase in the ubiquitin-mediated proteolysis pathway (UMP). To understand how the APC/C was targeted to its substrates, we performed a detailed analysis of one of the APC/C components, Cdc23p. In live cells, Cdc23-GFP localized to punctate nuclear spots surrounded by homogenous nuclear signal throughout the cell cycle. These punctate spots colocalized with two outer kinetochore proteins, Slk19p and Okp1p, but not with the spindle pole body protein, Spc42p. In late anaphase, the Cdc23-GFP was also visualized along the length of the mitotic spindle. We hypothesized that spindle checkpoint activation may affect the APC/C nuclear spot localization. Localization of Cdc23-GFP was disrupted upon nocodazole treatment in the kinetochore mutant okp1-5 and in the cdc20-1 mutant. Cdc23-GFP nuclear spot localization was not affected in the ndc10-1 mutant, which is defective in spindle checkpoint function. Additional studies using a mad2Delta strain revealed a microtubule dependency of Cdc23-GFP spot localization, whether or not the checkpoint response was activated. On the basis of these data, we conclude that Cdc23p localization was dependent on microtubules and was affected by specific types of kinetochore disruption.
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PMID:Changes in the localization of the Saccharomyces cerevisiae anaphase-promoting complex upon microtubule depolymerization and spindle checkpoint activation. 1528 Feb 25

The APC (anaphase-promoting complex) is a multisubunit E3 ubiquitin ligase that targets cell-cycle-related proteins for degradation by the 26 S proteasome. The APC contains at least 13 subunits and is regulated by the binding of co-activator proteins and by phosphorylation. It is not known why the APC contains 13 subunits when many other ubiquitin ligases are small single-subunit enzymes. In the present study, the structures and functions of individual APC subunits are discussed. By dissecting the roles of its parts, we hope to gain insight into the mechanism of the intact APC.
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PMID:The anaphase-promoting complex (APC): the sum of its parts? 1549 98

Neuronal plasticity relies on tightly regulated control of protein levels at synapses. One mechanism to control protein abundance is the ubiquitin-proteasome degradation system. Recent studies have implicated ubiquitin-mediated protein degradation in synaptic development, function, and plasticity, but little is known about the regulatory mechanisms controlling ubiquitylation in neurons. In contrast, ubiquitylation has long been studied as a central regulator of the eukaryotic cell cycle. A critical mediator of cell-cycle transitions, the anaphase-promoting complex/cyclosome (APC/C), is an E3 ubiquitin ligase. Although the APC/C has been detected in several differentiated cell types, a functional role for the complex in postmitotic cells has been elusive. We describe a novel postmitotic role for the APC/C at Drosophila neuromuscular synapses: independent regulation of synaptic growth and synaptic transmission. In neurons, the APC/C controls synaptic size via a downstream effector Liprin-alpha; in muscles, the APC/C regulates synaptic transmission, controlling the concentration of a postsynaptic glutamate receptor.
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PMID:Independent regulation of synaptic size and activity by the anaphase-promoting complex. 1555 Feb 51

Expression of the human T lymphotropic virus type I (HTLV-I) transactivator/oncoprotein, Tax, leads to faulty mitosis as reflected by chromosome aneuploidy, cytokinesis failure, and formation of micro- and multinucleated cells. Here we show that HTLV-I-transformed T cells progress through S/G(2)/M phases of the cell cycle with a delay. This delay is correlated with a decrease in the levels of cyclin A, cyclin B1, and securin. In tax-expressing cells, the Cdc20-associated anaphase promoting complex (APC(Cdc20)), an E3 ubiquitin ligase that controls metaphase to anaphase transition, becomes active before cellular entry into mitosis as evidenced by premature cyclin B1 polyubiquitination and degradation during S/G(2). Consistent with the notion that Tax activates APC(Cdc20) directly, Tax is found to coimmunoprecipitate with Cdc20 and Cdc27/APC3. The APC(Cdc20) activity prematurely activated by Tax remains sensitive to spindle checkpoint inhibition. Unscheduled activation of APC(Cdc20) by Tax provides an explanation for the mitotic abnormalities in HTLV-I-infected cells and is likely to play an important role in the development of adult T cell leukemia.
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PMID:HTLV-I Tax directly binds the Cdc20-associated anaphase-promoting complex and activates it ahead of schedule. 1562 61

Protein ubiquitination has critical roles in neuronal physiology and defects in protein ubiquitination have been implicated in neurodegenerative pathology. The anaphase-promoting complex/cyclosome (APC/C) is one of two key E3 ubiquitin ligase complexes that functions in regulating cell cycle transitions in proliferating cells by acting on cyclins and components of the mitotic/meiotic apparatus. Documentation of APC/C's action beyond cell division is sparse. In the past year, however, novel and surprising roles for APC/C in postmitotic neurons, particularly in the modulation of axonal growth and synaptic functions, have been revealed. APC/C and its activator Cdh-1 are found in good abundance in neurons, and these seem to function at different cellular locations, modulating apparently diverse processes such as axonal growth and synaptic function. Interestingly, there also appears to be a single link to these apparently divergent actions of APC/C in neurons--the multi-domain, multi-functional scaffolding protein Liprin-alpha which is an APC/C substrate.
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PMID:APC/C regulation of axonal growth and synaptic functions in postmitotic neurons: the Liprin-alpha connection. 1592 62

The anaphase-promoting complex or cyclosome (APC/C) is a multiprotein subunit E3 ubiquitin ligase complex that controls segregation of chromosomes and exit from mitosis in eukaryotes. It triggers elimination of key cell cycle regulators such as securin and mitotic cyclins during mitosis by polyubiquitinating them for proteasome degradation. Seven core subunit homologs of APC/C (APC1, APC2, APC11, CDC16, CDC23, CDC27, and DOC1) were identified in the Trypanosoma brucei genome data base. Expression of six of them was individually ablated by RNA interference in both the procyclic and bloodstream forms of T. brucei. Only the CDC27- and APC1-depleted cells were enriched in the G2/M phase with inhibited growth. Further studies indicated that T. brucei APC1 and CDC27 failed to complement the corresponding deletion mutants of budding yeast. However, their depletion from procyclic-form T. brucei enriched cells with two kinetoplasts and an enlarged nucleus possessing short metaphase-like mitotic spindles, suggesting that APC1 and CDC27 may play essential roles in promoting anaphase in the procyclic form. Their depletion from the bloodstream form, however, enriched cells with two kinetoplasts and two nuclei connected through a microtubule bundle, suggesting a late anaphase arrest. This is the first time functional APC/C subunit homologs were identified in T. brucei. The apparent differential activities of this putative APC/C in two distinct developmental stages suggest an unusual function. The apparent lack of functional involvement of some of the other individual structural subunit homologs of APC/C may indicate the structural uniqueness of T. brucei APC/C.
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PMID:Depletion of anaphase-promoting complex or cyclosome (APC/C) subunit homolog APC1 or CDC27 of Trypanosoma brucei arrests the procyclic form in metaphase but the bloodstream form in anaphase. 1599 9

The anaphase promoting complex/cyclosome (APC/C) is an E3 ubiquitin ligase that targets regulators of the cell division cycle for degradation by the 26S proteasome. Discovered as a key regulator of mitosis, the APC/C has more recently been recognized to also play a limiting role in the control of G(0) maintenance, G(1)/S-transition and DNA-replication. Human cytomegalovirus (HCMV) has been shown to interfere with cell cycle regulation at different levels. It can induce an S phase-prone proliferation program in quiescent cells but at the same time this virus directly inhibits competitive cellular DNA replication. Here we show, that human cytomegalovirus (HCMV) inactivates the G(0)/G(1) APC/C rapidly after infection of quiescent fibroblasts, resulting in the untimely stabilization of APC/C substrates. APC/C inactivation is caused by the dissociation of its positive regulator, Cdh1. Surprisingly, this dissociation is independent from known Cdh1 inhibitors, Emi1 and Cyclin A, suggesting that APC/C-Cdh1 inhibition by HCMV is directly caused by a viral protein or an intermediate cellular factor distinct from Emi1 and Cyclin A. Thus, upon infection of quiescent cells HCMV not only activates the E2F-dependent G(1)/S transcription program but also facilitates protein accumulation of APC/C substrates by rapid Cdh1 dissociation.
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PMID:Human cytomegalovirus inactivates the G0/G1-APC/C ubiquitin ligase by Cdh1 dissociation. 1613 13


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