BUB1B
Domain
The D-box targets the protein for rapid degradation by ubiquitin-dependent proteolysis during the transition from mitosis to interphase.
The BUB1 N-terminal domain directs kinetochore localization and binding to BUB3.
Function
Essential component of the mitotic checkpoint. Required for normal mitosis progression. The mitotic checkpoint delays anaphase until all chromosomes are properly attached to the mitotic spindle. One of its checkpoint functions is to inhibit the activity of the anaphase-promoting complex/cyclosome (APC/C) by blocking the binding of CDC20 to APC/C, independently of its kinase activity. The other is to monitor kinetochore activities that depend on the kinetochore motor CENPE. Required for kinetochore localization of CENPE. Negatively regulates PLK1 activity in interphase cells and suppresses centrosome amplification. Also implicated in triggering apoptosis in polyploid cells that exit aberrantly from mitotic arrest. May play a role for tumor suppression.
Involvement in disease
Defects in BUB1B are associated with tumor formation.
Premature chromatid separation trait
PCS
Consists of separate and splayed chromatids with discernible centromeres and involves all or most chromosomes of a metaphase. It is found in up to 2% of metaphases in cultured lymphocytes from approximately 40% of normal individuals. When PCS is present in 5% or more of cells, it is known as the heterozygous PCS trait and has no obvious phenotypic effect, although some have reported decreased fertility. Inheritance is autosomal dominant.
None
The disease is caused by variants affecting the gene represented in this entry.
Mosaic variegated aneuploidy syndrome 1
MVA1
A severe developmental disorder characterized by mosaic aneuploidies, predominantly trisomies and monosomies, involving multiple different chromosomes and tissues. Affected individuals typically present with severe intrauterine growth retardation and microcephaly. Eye anomalies, mild dysmorphism, variable developmental delay, and a broad spectrum of additional congenital abnormalities and medical conditions may also occur. The risk of malignancy is high, with rhabdomyosarcoma, Wilms tumor and leukemia reported in several cases.
None
The disease is caused by variants affecting the gene represented in this entry. MVA1 is caused by biallelic mutations in the BUB1B gene.
Post-translational modifications
Proteolytically cleaved by caspase-3 in a cell cycle specific manner. The cleavage might be involved in the durability of the cell cycle delay. Caspase-3 cleavage is associated with abrogation of the mitotic checkpoint. The major site of cleavage is at Asp-610.
Acetylation at Lys-250 regulates its degradation and timing in anaphase entry.
Ubiquitinated. Degraded by the proteasome (PubMed:19407811). Ubiquitinated by UBR5, promoting disassembly of the mitotic checkpoint complex from the APC/C complex (PubMed:35217622).
Sumoylated with SUMO2 and SUMO3. The sumoylation mediates the association with CENPE at the kinetochore.
Autophosphorylated in vitro. Intramolecular autophosphorylation is stimulated by CENPE. Phosphorylated during mitosis and hyperphosphorylated in mitotically arrested cells. Phosphorylation at Ser-670 and Ser-1043 occurs at kinetochores upon mitotic entry with dephosphorylation at the onset of anaphase.
Sequence Similarities
Belongs to the protein kinase superfamily. Ser/Thr protein kinase family. BUB1 subfamily.
Tissue Specificity
Highly expressed in thymus followed by spleen. Preferentially expressed in tissues with a high mitotic index.
Cellular localization
- Cytoplasm
- Nucleus
- Chromosome
- Centromere
- Kinetochore
- Cytoplasm
- Cytoskeleton
- Microtubule organizing center
- Centrosome
- Cytoplasmic in interphase cells. Associates with the kinetochores in early prophase. Kinetochore localization requires BUB1, PLK1 and KNL1.
Alternative names
BUBR1, MAD3L, SSK1, BUB1B, Mitotic checkpoint serine/threonine-protein kinase BUB1 beta, MAD3/BUB1-related protein kinase, Mitotic checkpoint kinase MAD3L, Protein SSK1, hBUBR1