BUB3

Budding uninhibited by benzimidazoles 3 homolog (yeast)
Identifiers
Symbols BUB3; BUB3L; hBUB3
External IDs OMIM603719 MGI1343463 HomoloGene3470 GeneCards: BUB3 Gene
RNA expression pattern
More reference expression data
Orthologs
Species Human Mouse
Entrez 9184 12237
Ensembl ENSG00000154473 ENSMUSG00000066979
UniProt O43684 Q6ZWM5
RefSeq (mRNA) NM_001007793.2 NM_009774.3
RefSeq (protein) NP_001007794.1 NP_033904.2
Location (UCSC) Chr 10:
124.91 – 124.92 Mb
Chr 7:
138.7 – 138.72 Mb
PubMed search [1] [2]

Mitotic checkpoint protein BUB3 is a protein that in humans is encoded by the BUB3 gene.[1][2]

Bub3 is a protein involved with the regulation of the Spindle Assembly Checkpoint (SAC); though BUB3 is non-essential in yeast, it is essential in higher eukaryotes. As one of the checkpoint proteins, Bub3 delays the irreversible onset of anaphase through direction of kinetochore localization during prometaphase[1] to achieve biorentation. In directing the kinetochore-microtubule interaction, this ensures the proper (and consequenctly, bioriented) attachment of the chromosomes prior to anaphase. Bub3 and its related proteins that form the Spindle Assembly Checkpoint (SAC) inhibit the action of the Anaphase Promoting Complex (APC), preventing early anaphase entry and mitotic exit; this serves as a mechanism for the fidelity of chromosomal segregation.[3]

Contents

Structure

The crystal structure of Bub3 indicates a protein of the seven-bladed beta-propeller structure with the presence of WD40 repeats, with each blade formed by four anti-parallel beta sheet strands that have been organized around a tapered channel. Mutation data suggest several important surfaces of interaction for the formation of the SAC, particularly the conserved tryptophans (in blades 1 and 3) and the conserved VAVE sequences in blade 5.

Rae1 (an mRNA export factor), another member of the WD40 protein family, shows high sequence conservation with that of Bub3. Both share a Gle2p-binding-sequence (GLEBS) motif; while Bub3 specifically binds Mad3 and Bub1, Rae1 has more promiscuous binding as it binds both the nuclear pore complex and Bub1. This indicates a similarity in interaction of Bub3 and Rae1 with Bub1.[4]

Interactions

BUB3 has been shown to interact with BUB1B,[1][5][6] HDAC1[7] and Histone deacetylase 2.[7]

Bub3 has been shown to form complexes with Mad1-Bub1 and with Cdc20 (the interaction of which does not require intact kinetochores). Additionally, it has been shown to bind Mad2 and Mad3.[8][9]

Bub3 directs the localization of Bub1 at the kinetochore in order to activate the SAC.[1] In both Saccharomyces cerevisiae and metazoans, Bub3 has been show to bind BubR1 and Bub1[10][11]

Bub3 also acts as a regulator in that it affects binding of Mad3 to Mad2.[9]

Structural and sequence analysis indicated the existence of three conserved regions that are referred to as WD40 repeats. Mutation of one of these motifs has indicated an impaired ability of Bub3 to interact with Mad2, Mad3, and Cdc20. The structural data suggested that Bub3 acts as a platform that mediates the interaction of SAC protein complexes.[4][9]

Role in the Spindle Assembly Checkpoint

At unattached kinetochores, a complex consisting of BubR1, Bub3, and Cdc20 interact with the Mad2-Cdc20 complex to inhibit the APC, thus inhibiting the formation of active APCCdc20.[12][13] Bub3 binds constitutively to Bub1; in this arrangement, Bub3 acts as a key component of the SAC in the formation of an inhibitory complex.[9] Securin and cyclin B are also stabilized before the anaphase transition by the unattached kinetochores.[14] The stabilization of cyclin and securin prevent the degradation that would lead to the irreversible and fast separation of the sister chromatids.

The formation of these “inhibitory complexes” and steps feed into a ‘wait’ signal before activation of separase; at the stage prior to anaphase, securin inhibits the activity of separase and maintains the cohesion complex.[3]

References

  1. ^ a b c d Taylor SS, Ha E, McKeon F (Aug 1998). "The human homologue of Bub3 is required for kinetochore localization of Bub1 and a Mad3/Bub1-related protein kinase". J Cell Biol 142 (1): 1–11. doi:10.1083/jcb.142.1.1. PMC 2133037. PMID 9660858. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2133037. 
  2. ^ "Entrez Gene: BUB3 BUB3 budding uninhibited by benzimidazoles 3 homolog (yeast)". http://www.ncbi.nlm.nih.gov/sites/entrez?Db=gene&Cmd=ShowDetailView&TermToSearch=9184. 
  3. ^ a b Morgan, David O (2007). The cell cycle: principles of control. London: Published by New Science Press in association with Oxford University Press. ISBN 0-87893-508-8. 
  4. ^ a b *Larsen, N.A., Harrison, S.C. (2004). "Crystal structure of the spindle assembly checkpoint protein Bub3". J Mol Biol 344 (4): 885–92. doi:10.1016/j.jmb.2004.09.094. PMID 15544799. 
  5. ^ *Sudakin, V; Chan G K, Yen T J (2001). "Checkpoint inhibition of the APC/C in HeLa cells is mediated by a complex of BUBR1, BUB3, CDC20, and MAD2". J. Cell Biol. 154 (5): 925–36. doi:10.1083/jcb.200102093. PMC 2196190. PMID 11535616. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2196190. 
  6. ^ *Cayrol, C., Cougoule, C., Wright, M. (2002). "The beta2-adaptin clathrin adaptor interacts with the mitotic checkpoint kinase BubR1". Biochem. Biophys. Res. Commun. 298 (5): 720–30. doi:10.1016/S0006-291X(02)02522-6. PMID 12419313. 
  7. ^ a b *Yoon, Y-M, Baek, K-H, Jeong, S-J, et al. (2004). "WD repeat-containing mitotic checkpoint proteins act as transcriptional repressors during interphase". FEBS Lett. 575 (1–3): 23–9. doi:10.1016/j.febslet.2004.07.089. PMID 15388328. 
  8. ^ *Logarinho, E., Bousbaa, H. (2008). "Kinetochore-microtubule interactions "in check" by Bub1, Bub3 and BubR1: The dual task of attaching and signalling". Cell Cycle 7 (12): 1763–1768. PMID 18594200. 
  9. ^ a b c d *Fraschini, R., Beretta, A., Sironi, L., Musacchio, A.,et al. (2001). "Bub3 interaction with Mad2, Mad3 and Cdc20 is mediated by WD40 repeats and does not require intact kinetochores". The EMBO Journal 20 (23): 6648–6659. doi:10.1093/emboj/20.23.6648. PMC 125326. PMID 11726501. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=125326. 
  10. ^ *Yu, H. (2002). "Regulation of APC–Cdc20 by the spindle checkpoint". Current Opinion in Cell Biology 14 (6): 706–714. doi:10.1016/S0955-0674(02)00382-4. PMID 12473343. 
  11. ^ *Doncic, A., Ben-Jacob, E., Einav, S., Barkai, N. (2009). Khanin, Raya. ed. "Reverse Engineering of the Spindle Assembly Checkpoint". PLoS ONE 4 (8): e6495. doi:10.1371/journal.pone.0006495. PMC 2714964. PMID 19652707. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2714964. 
  12. ^ *Eytan, E., Braunstein, I., Ganoth, D., et al. (2008). "Two different mitotic checkpoint inhibitors of the anaphase-promoting complex/cyclosome antagonize the action of the activator Cdc20". Proc Natl Acad Sci USA 105 (7): 9181–9185. doi:10.1073/pnas.0804069105. PMC 2453698. PMID 18591651. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2453698. 
  13. ^ *Fang G, Yu H and Kirschner MW (1998). "Direct binding of CDC20 protein family members activates the anaphase-promoting complex in mitosis and G1". Mol Cell 2 (2): 163–171. doi:10.1016/S1097-2765(00)80126-4. PMID 9734353. 
  14. ^ *Li, M., Li, S., Yuan, J., Wang, Z-B, Sun, S-C, et al. (2009). Jin, Dong-Yan. ed. "Bub3 Is a Spindle Assembly Checkpoint Protein Regulating Chromosome Segregation during Mouse Oocyte Meiosis". PLoS ONE 4 (11): e7701. doi:10.1371/journal.pone.0007701. PMC 2765619. PMID 19888327. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2765619. 

Further reading