Mitotic checkpoint protein BUB3

BUB3 (mitotic checkpoint protein BUB3) is a 328-amino-acid protein that functions in spindle-assembly checkpoint signaling and kinetochore-microtubule attachment regulation (UniProt: O43684). It works with BUB1 to establish stable bipolar chromosome attachments and inhibits the anaphase-promoting complex (APC/C) during mitotic checkpoint activation by phosphorylating CDC20 and MAD1L1. The protein is thus central to accurate chromosome segregation in both mitosis and oocyte meiosis.

BUB3 operates primarily at kinetochores and in cell-cycle regulatory pathways. No disease associations are documented in UniProt's curated records for this protein. However, BUB3 is present in human post-mortem brain tissue and participates in fundamental cell-cycle processes relevant to cellular homeostasis.

In Alzheimer's Disease, BUB3 is upregulated in post-mortem AD brain compared to age-matched controls (Chaparral AD proteomics), with a mean log2 fold-change of +0.43 across one subcellular fraction in TMT-labeled proteomic analysis. This elevation may reflect altered cell-cycle checkpoint activity or cellular stress responses in AD pathology, though the biological significance remains to be determined.