|
|
|
||||
| Home Help Feedback Subscriptions Archive Search Table of Contents | |||||
First published online June 8, 2006
doi: 10.1242/10.1242/jcs.02937
Cell Science at a Glance |
Wellcome Trust/Cancer Research UK Gurdon Institute, Tennis Court Road, Cambridge, CB2 1QN, UK
* Author for correspondence (e-mail: c.acquaviva{at}gurdon.cam.ac.uk)
| Introduction |
|---|
|
|
|---|
| The APC/C in the ubiquitin-proteasome pathway |
|---|
|
|
|---|
The APC/C is a RING-type E3. These contain a RING zinc-finger domain that binds the E2 and both recruits the E2 to the substrate and acts as a cofactor to enhance substrate modification.
| APC/C regulation |
|---|
|
|
|---|
|
Two meiosis-specific activators of the APC/C have been identified in yeast: (1) Schizosaccharomyces pombe Mfr1, which functions at the end of meiosis II and degrades the remaining B-type cyclin (Cdc13) to reduce Cdk (Cdc2) activity (Blanco et al., 2001
); and (2) Ama1, a Saccharomyces cerevisiae Cdc20 family member that is specifically expressed in meiosis and important for the first meiotic division. Drosophila has two meiosis-specific APC/C activators: Fzr2 and Cortex, which are exclusively expressed during spermatogenesis and oogenesis, respectively.
APC/C inhibitors
Before entry into mitosis, the APC/C must be inhibited to allow accumulation of mitotic cyclin-Cdk complexes. In animal cells, this is in part due to the F-box protein Rca1/Emi1. This protein probably blocks association of the APC/C with substrates. RCA1 in Drosophila interacts with Cdh1; Emi1, its mammalian homologue, can also bind Cdc20 in vitro. At the beginning of mitosis, Emi1 is phosphorylated and degraded by an Skp1-Cullin-F-box protein (SCF) E3 ligase complex. A relative of Emi1, Emi2/XErp1 appears to inhibit APC/CCdc20 in Xenopus meiosis II (Schmidt et al., 2005
).
Mes1 is a meiosis-specific inhibitor of the APC/C in S. pombe. It directly binds and inhibits Slp1 (Cdc20) but has a function distinct from that of the checkpoint protein Mad2 (see below). Mes1 blocks the complete degradation of the B-type cyclin Cdc13 at anaphase I, allowing sufficient kinase activity to remain to initiate meiosis II. It is not clear what controls Mes1 activity (Izawa et al., 2005
).
RASSF1A is a tumour suppressor that can interact with Cdc20 and inhibit the APC/C (Song et al., 2005
). It might prevent premature cyclin degradation before the spindle checkpoint is set up; how its function is regulated is currently unclear.
The spindle assembly checkpoint
The spindle assembly checkpoint ensures that sister chromatids are equally divided between the two daughter cells at anaphase, blocking sister separation until each pair is correctly attached to microtubules emanating from opposite poles of the spindle. In mitosis, this checkpoint inhibits anaphase by preventing cyclin B and securin degradation, and responds to a signal generated by any improperly attached kinetochore. The ultimate mediators of this checkpoint are the checkpoint proteins Mad2 and BubR1 - as part of independent complexes or a single inhibitory complex called the mitotic checkpoint complex (MCC) that can bind Cdc20 (Bharadwaj and Yu, 2004
; Musacchio and Hardwick, 2002
; Yu, 2002
; Zhou et al., 2002
). The exact mechanism of APC/C inhibition is unclear, as is whether the APC/C could be modified by this signal. APC/C interacts with checkpoint proteins (Wassmann and Benezra, 1998
) and co-localises with the checkpoint signal (Acquaviva et al., 2004
).
In Xenopus, two other proteins are implicated in APC/C regulation. The ubiquitin ligase Xnf7, which binds and inhibits the APC/C (Casaletto et al., 2005
), and Mad2L2, a relative of Mad2, which inhibits APC/CCdh1 in vitro (Pfleger et al., 2001
). However, it is not clear whether these proteins have a conserved function.
Regulation of the APC/C by phosphorylation
A recent mass spectroscopy analysis of the complex in mammalian cells showed 42 phosphorylation sites, 34 of them mitosis specific (Kraft et al., 2003
). In Xenopus, phosphatase treatment of extracts prevents APC/C activity, and mutation of potential Cdk1 phosphorylation sites in three budding yeast APC/C subunits delays progression through mitosis (Rudner and Murray, 2000
). One function of phosphorylation is to regulate association with Cdc20. Other phosphorylations might finely tune APC/C activity. The main kinases involved are Cdk1 and polo-like kinase 1 (Plk1). In fission yeast, protein kinase A (PKA) negatively regulates APC/C but this might not be true elsewhere (Kraft et al., 2003
). Clearly, other kinases could also be involved, such as those that are part of the mitotic checkpoint.
| APC/C complex composition |
|---|
|
|
|---|
The catalytic core
APC2 and APC11 form the enzymatic core of the complex. They harbour a cullin and a RING-finger domain, respectively. By analogy to the structure of the SCF, APC2 and APC11 could form a two-subunit catalytic core that binds the E2. In vitro, APC2 and APC11 can transfer ubiquitin to a substrate, but this reaction has little substrate specificity and poor processivity.
`TPR' subunits
Four subunits - APC3, APC6, APC7 and APC8 - have several tetratricopeptide repeat (TPR) protein-protein interaction motifs. In vitro, those of APC3 and APC7 interact with the IR motifs of Cdc20 and Cdh1. Moreover, the four TPR subunits contain most of the phosphorylation sites present in the APC/C (Kraft et al., 2003
).
Structural components
Some subunits could have a scaffolding role. APC4 and APC5 might connect the enzymatic core to the `regulatory' TPR subunits. However, these proteins might not necessarily be limited to such a role. APC9 (in yeast), Cdc26 and APC13 also seem to be required for the structure and/or stability of the APC/C. APC13 is more unusual because it seems to provide an essential meiosis-specific function (Hall et al., 2003
; Passmore et al., 2003
).
APC10
APC10 is not essential for the assembly of the APC/C but is required for APC/C activity in yeast. APC10 contains a DOC domain; these are found in several proteins involved in ubiquitylation reactions. APC10 could bind the APC/C through its interaction with APC3 via an IR motif. It could also be involved in substrate recognition (Carroll et al., 2005
; Passmore et al., 2003
) and has been implicated in the processivity of ubiquitylation (Carroll and Morgan, 2002
).
APC15
Mnd2/APC15 is associated with the APC/C in proliferating cells and in meiosis until metaphase II but its role seems to be specific to meiosis. It prevents premature degradation of securin by APC/CAma1 and thus premature loss of cohesion in meiosis I. Its inhibitory activity might be regulated by phosphorylation in metaphase I, and degradation in anaphase. How it discriminates between Ama1 and the other APC/C activators is unknown (Hall et al., 2003
; Oelschlaegel et al., 2005
; Penkner et al., 2005
).
| The role of APC/C in mitosis and meiosis |
|---|
|
|
|---|
The APC/C also induces the degradation of several proteins from prophase to telophase in mitosis, including motor proteins and kinases, and possibly Shugoshin (Sgo1), which is involved in protecting sister chromatid cohesion at the centromeres, (Pines, 2006
; Wang and Dai, 2005
). However, the requirement for protein degradation has only been addressed in a few cases.
APC/CCdh1-dependent degradation of the cyclins in G1 phase prevents the premature accumulation of these proteins and premature entry into S phase. Moreover, APC/CCdh1 controls the degradation of other regulators of S phase (e.g. Orc1, Cdc6 and geminin) to regulate replication origin assembly. Finally, the APC/C also inhibits the activity of the SCF E3 that controls the G1-S transition. One of its components, the F-box protein Skp2, is a substrate for the APC/C in cycling cells (Vodermaier, 2004
).
Meiosis
Between meiosis I and meiosis II, Cdk activity and Cdc20 protein levels must be maintained and/or restored. In yeast, Mes1 protects part of the cyclin B population from degradation. In Xenopus, 50-70% of cyclin B1 is protected from degradation in meiosis I through an unknown mechanism.
To ensure chromosome pairs and sister chromatids separate at distinct stages, meiosis I and meiosis II employ different cohesin complexes (Rec8 and Scc1), factors protecting specific cohesin regions (Sgo1) and specific activators of the APC/C (Ama1 in S. cerevisae, Mfr1/Fzr1 in S. pombe, Fzr2 and Cortex in Drosophila, Cdh1 in mouse).
In vertebrates, meiosis II is characterised by a prolonged metaphase arrest. This is imposed by cytostatic factor (CSF), which is proposed to inhibit the APC/C and involves Emi2/XErp1 and/or Emi1 in Xenopus oocytes (Schmidt et al., 2005
).
| Substrate recognition |
|---|
|
|
|---|
Substrate recognition by the APC/C is probably not dependent only on Cdc20 and Cdh1. During the embryonic Drosophila cell cycle, no Cdh1 is expressed but degradation of specific substrates is still temporally regulated. Moreover, substrates of Cdc20 or Cdh1 do not all disappear at the same time in mitosis - for example, APC/CCdc20 ubiquitylates cyclin A in prometaphase before cyclin B in metaphase. Other subunits of the APC/C, such as APC10, might therefore be involved in substrate selection. Indeed, the cyclin B D-Box motif and the APC/C directly interact in Xenopus egg extracts (Yamano et al., 2004
) and in S. pombe (Meyn et al., 2002
). Substrates might thus cooperatively bind to Cdc20 or Cdh1 and the APC/C itself.
Strong evidence indicates that regulation of the localisation of substrates and the APC/C participates in substrate selection. In Drosophila and human cells, cyclin B degradation is spatially regulated and it appears to be localised to the spindle (Clute and Pines, 1999
; Huang and Raff, 1999
; Huang and Raff, 2002
). Moreover, the subcellular localisation of the APC/C is regulated (Acquaviva et al., 2004
; Huang and Raff, 2002
; Melloy and Holloway, 2004
; Topper et al., 2002
; Yen, 2002
) and the inhibitory signal from the spindle assembly checkpoint could be restricted to specific cellular locations (Musacchio and Hardwick, 2002
; Yen, 2002
).
| Perspectives |
|---|
|
|
|---|
| References |
|---|
|
|
|---|
Acquaviva, C., Herzog, F., Kraft, C. and Pines, J. (2004). The anaphase promoting complex/cyclosome is recruited to centromeres by the spindle assembly checkpoint. Nat. Cell Biol. 6, 892-898.[CrossRef][Medline]
Bharadwaj, R. and Yu, H. (2004). The spindle checkpoint, aneuploidy, and cancer. Oncogene 23, 2016-2027.[CrossRef][Medline]
Blanco, M. A., Pelloquin, L. and Moreno, S. (2001). Fission yeast mfr1 activates APC and coordinates meiotic nuclear division with sporulation. J. Cell Sci. 114, 2135-2143.
Carroll, C. W. and Morgan, D. O. (2002). The Doc1 subunit is a processivity factor for the anaphase-promoting complex. Nat. Cell Biol. 4, 880-887.[CrossRef][Medline]
Carroll, C. W., Enquist-Newman, M. and Morgan, D. O. (2005). The APC subunit Doc1 promotes recognition of the substrate destruction box. Curr. Biol. 15, 11-18.[CrossRef][Medline]
Casaletto, J. B., Nutt, L. K., Wu, Q., Moore, J. D., Etkin, L. D., Jackson, P. K., Hunt, T. and Kornbluth, S. (2005). Inhibition of the anaphase-promoting complex by the Xnf7 ubiquitin ligase. J. Cell Biol. 169, 61-71.
Castro, A., Bernis, C., Vigneron, S., Labbe, J. C. and Lorca, T. (2005). The anaphase-promoting complex: a key factor in the regulation of cell cycle. Oncogene 24, 314-325.[CrossRef][Medline]
Clute, P. and Pines, J. (1999). Temporal and spatial control of cyclin B1 destruction in metaphase. Nat. Cell Biol. 1, 82-87.[CrossRef][Medline]
Dube, P., Herzog, F., Gieffers, C., Sander, B., Riedel, D., Muller, S. A., Engel, A., Peters, J. M. and Stark, H. (2005). Localization of the coactivator Cdh1 and the cullin subunit Apc2 in a cryo-electron microscopy model of vertebrate APC/C. Mol. Cell 20, 867-879.[CrossRef][Medline]
Farras, R., Bossis, G., Andermarcher, E., Jariel-Encontre, I. and Piechaczyk, M. (2005). Mechanisms of delivery of ubiquitylated proteins to the proteasome: new target for anti-cancer therapy? Crit. Rev. Oncol. Hematol. 54, 31-51.[Medline]
Gieffers, C., Peters, B. H., Kramer, E. R., Dotti, C. G. and Peters, J. M. (1999). Expression of the CDH1-associated form of the anaphase-promoting complex in postmitotic neurons. Proc. Natl. Acad. Sci. USA 96, 11317-11322.
Hall, M. C., Torres, M. P., Schroeder, G. K. and Borchers, C. H. (2003). Mnd2 and Swm1 are core subunits of the Saccharomyces cerevisiae anaphase-promoting complex. J. Biol. Chem. 278, 16698-16705.
Huang, J. and Raff, J. W. (1999). The disappearance of cyclin B at the end of mitosis is regulated spatially in Drosophila cells. EMBO J. 18, 2184-2195.[CrossRef][Medline]
Huang, J. Y. and Raff, J. W. (2002). The dynamic localisation of the Drosophila APC/C: evidence for the existence of multiple complexes that perform distinct functions and are differentially localised. J. Cell Sci. 115, 2847-2856.
Izawa, D., Goto, M., Yamashita, A., Yamano, H. and Yamamoto, M. (2005). Fission yeast Mes1p ensures the onset of meiosis II by blocking degradation of cyclin Cdc13p. Nature 434, 529-533.[CrossRef][Medline]
Kraft, C., Herzog, F., Gieffers, C., Mechtler, K., Hagting, A., Pines, J. and Peters, J. M. (2003). Mitotic regulation of the human anaphase-promoting complex by phosphorylation. EMBO J. 22, 6598-6609.[CrossRef][Medline]
Melloy, P. G. and Holloway, S. L. (2004). Changes in the localization of the Saccharomyces cerevisiae anaphase-promoting complex upon microtubule depolymerization and spindle checkpoint activation. Genetics 167, 1079-1094.
Meyn, M. A., 3rd, Melloy, P. G., Li, J. and Holloway, S. L. (2002). The destruction box of the cyclin Clb2 binds the anaphase-promoting complex/cyclosome subunit Cdc23. Arch. Biochem. Biophys. 407, 189-195.[CrossRef][Medline]
Musacchio, A. and Hardwick, K. G. (2002). The spindle checkpoint: structural insights into dynamic signalling. Nat. Rev. Mol. Cell Biol. 3, 731-741.[CrossRef][Medline]
Oelschlaegel, T., Schwickart, M., Matos, J., Bogdanova, A., Camasses, A., Havlis, J., Shevchenko, A. and Zachariae, W. (2005). The yeast APC/C subunit Mnd2 prevents premature sister chromatid separation triggered by the meiosis-specific APC/C-Ama1. Cell 120, 773-788.[CrossRef][Medline]
Passmore, L. A., McCormack, E. A., Au, S. W., Paul, A., Willison, K. R., Harper, J. W. and Barford, D. (2003). Doc1 mediates the activity of the anaphase-promoting complex by contributing to substrate recognition. EMBO J. 22, 786-796.[CrossRef][Medline]
Passmore, L. A., Booth, C. R., Venien-Bryan, C., Ludtke, S. J., Fioretto, C., Johnson, L. N., Chiu, W. and Barford, D. (2005). Structural analysis of the anaphase-promoting complex reveals multiple active sites and insights into polyubiquitylation. Mol. Cell 20, 855-866.[CrossRef][Medline]
Penkner, A. M., Prinz, S., Ferscha, S. and Klein, F. (2005). Mnd2, an essential antagonist of the anaphase-promoting complex during meiotic prophase. Cell 120, 789-801.[CrossRef][Medline]
Peters, J. M. (1998). SCF and APC: the Yin and Yang of cell cycle regulated proteolysis. Curr. Opin. Cell Biol. 10, 759-768.[CrossRef][Medline]
Peters, J. M. (2002). The anaphase-promoting complex: proteolysis in mitosis and beyond. Mol. Cell 9, 931-943.[CrossRef][Medline]
Pfleger, C. M., Salic, A., Lee, E. and Kirschner, M. W. (2001). Inhibition of Cdh1-APC by the MAD2-related protein MAD2L2: a novel mechanism for regulating Cdh1. Genes Dev. 15, 1759-1764.
Pickart, C. M. (2004). Back to the future with ubiquitin. Cell 116, 181-190.[CrossRef][Medline]
Pines, J. (2006). Mitosis: a matter of getting rid of the right protein at the right time. Trends Cell Biol. 16, 55-63.[CrossRef][Medline]
Rudner, A. D. and Murray, A. W. (2000). Phosphorylation by Cdc28 activates the Cdc20-dependent activity of the anaphase-promoting complex. J. Cell Biol. 149, 1377-1390.
Schmidt, A., Duncan, P. I., Rauh, N. R., Sauer, G., Fry, A. M., Nigg, E. A. and Mayer, T. U. (2005). Xenopus polo-like kinase Plx1 regulates XErp1, a novel inhibitor of APC/C activity. Genes Dev. 19, 502-513.
Song, M. S., Chang, J. S., Song, S. J., Yang, T. H., Lee, H. and Lim, D. S. (2005). The centrosomal protein RAS association domain family protein 1A (RASSF1A)-binding protein 1 regulates mitotic progression by recruiting RASSF1A to spindle poles. J. Biol. Chem. 280, 3920-3927.
Teng, F. Y. and Tang, B. L. (2005). APC/C regulation of axonal growth and synaptic functions in postmitotic neurons: the Liprin-alpha connection. Cell. Mol. Life Sci. 62, 1571-1578.[CrossRef][Medline]
Thornton, B. R., Ng, T. M., Matyskiela, M. E., Carroll, C. W., Morgan, D. O. and Toczyski, D. P. (2006). An architectural map of the anaphase-promoting complex. Genes Dev. 20, 449-460.
Topper, L. M., Campbell, M. S., Tugendreich, S., Daum, J. R., Burke, D. J., Hieter, P. and Gorbsky, G. J. (2002). The dephosphorylated form of the anaphase-promoting complex protein Cdc27/Apc3 concentrates on kinetochores and chromosome arms in mitosis. Cell Cycle 1, 282-292.[Medline]
van Roessel, P., Elliott, D. A., Robinson, I. M., Prokop, A. and Brand, A. H. (2004). Independent regulation of synaptic size and activity by the anaphase-promoting complex. Cell 119, 707-718.[CrossRef][Medline]
Vodermaier, H. C. (2004). APC/C and SCF: controlling each other and the cell cycle. Curr. Biol. 14, R787-R796.[CrossRef][Medline]
Vodermaier, H. C., Gieffers, C., Maurer-Stroh, S., Eisenhaber, F. and Peters, J. M. (2003). TPR subunits of the anaphase-promoting complex mediate binding to the activator protein CDH1. Curr. Biol. 13, 1459-1468.[CrossRef][Medline]
Wang, X. and Dai, W. (2005). Shugoshin, a guardian for sister chromatid segregation. Exp. Cell Res. 310, 1-9.[CrossRef][Medline]
Wassmann, K. and Benezra, R. (1998). Mad2 transiently associates with an APC/p55Cdc complex during mitosis. Proc. Natl. Acad. Sci. USA 95, 11193-11198.
Wirth, K. G., Ricci, R., Gimenez-Abian, J. F., Taghybeeglu, S., Kudo, N. R., Jochum, W., Vasseur-Cognet, M. and Nasmyth, K. (2004). Loss of the anaphase-promoting complex in quiescent cells causes unscheduled hepatocyte proliferation. Genes Dev. 18, 88-98.
Yamano, H., Gannon, J., Mahbubani, H. and Hunt, T. (2004). Cell cycle-regulated recognition of the destruction box of cyclin B by the APC/C in Xenopus egg extracts. Mol. Cell 13, 137-147.[CrossRef][Medline]
Yen, T. J. (2002). The complexity of APC/C regulation: location, location, location. Cell Cycle 1, 260-261.[Medline]
Yu, H. (2002). Regulation of APC-Cdc20 by the spindle checkpoint. Curr. Opin. Cell Biol. 14, 706-714.[CrossRef][Medline]
Zhou, J., Yao, J. and Joshi, H. C. (2002). Attachment and tension in the spindle assembly checkpoint. J. Cell Sci. 115, 3547-3555.
This article has been cited by other articles:
![]() |
F. Gergely and R. Basto Multiple centrosomes: together they stand, divided they fall Genes & Dev., September 1, 2008; 22(17): 2291 - 2296. [Abstract] [Full Text] [PDF] |
||||
![]() |
B. E. Keyes, C. M. Yellman, and D. J. Burke Differential Regulation of Anaphase Promoting Complex/Cyclosome Substrates by the Spindle Assembly Checkpoint in Saccharomyces cerevisiae Genetics, January 1, 2008; 178(1): 589 - 591. [Abstract] [Full Text] [PDF] |
||||
![]() |
E. R. Griffis, N. Stuurman, and R. D. Vale Spindly, a novel protein essential for silencing the spindle assembly checkpoint, recruits dynein to the kinetochore J. Cell Biol., July 30, 2007; 177(6): 1005 - 1015. [Abstract] [Full Text] [PDF] |
||||
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||