BubR1 acetylation at prometaphase is required for modulating APC/C activity and timing of mitosis

Abstract

Regulation of BubR1 is central to the control of APC/C activity. We have found that BubR1 forms a complex with PCAF and is acetylated at lysine 250. Using mass spectrometry and acetylated BubR1-specific antibodies, we have confirmed that BubR1 acetylation occurs at prometaphase. Importantly, BubR1 acetylation was required for checkpoint function, through the inhibition of ubiquitin-dependent BubR1 degradation. BubR1 degradation began before the onset of anaphase. It was noted that the pre-anaphase degradation was regulated by BubR1 acetylation. Degradation of an acetylation-mimetic form, BubR1–K250Q, was inhibited and chromosome segregation in cells expressing BubR1–K250Q was markedly delayed. By contrast, the acetylation-deficient mutant, BubR1–K250R, was unstable, and mitosis was accelerated in BubR1–K250R-expressing cells. Furthermore, we found that APC/C–Cdc20 was responsible for BubR1 degradation during mitosis. On the basis of our collective results, we propose that the acetylation status of BubR1 is a molecular switch that converts BubR1 from an inhibitor to a substrate of the APC/C complex, thus providing an efficient way to modulate APC/C activity and mitotic timing.

Sirt2‐BubR1 acetylation pathway mediates the effects of advanced maternal age on oocyte quality

“…Substitution of lysine (K) with a glutamine (Q) mimics an acetylated amino acid state, while substitution with an arginine (R) mimics deacetylation (Choi et al., 2009). Immunoblotting verified that exogenous BubR1 protein was efficiently overexpressed in mouse oocytes (Figure 2a–b), and the various mutant BubR1 proteins were expressed to the similar extent (Figure 2c).…”

“…Of note, BubR1 was identified to be acetylated at K250 at prometaphase in human cells. Chromosome segregation in cells expressing BubR1‐K250Q was delayed, whereas mitotic progression was accelerated in cells expressing BubR1‐K250R (Choi et al., 2009). Loss of BubR1 acetylation causes defects in SAC signaling and promotes tumor formation in mice (Park et al., 2013).…”

“…In specific, Sirt2 was shown to be able to modulate BubR1 stability in vitro and in vivo through deacetylation (North et al., 2014; Suematsu et al., 2014). Moreover, numerous studies demonstrated that deacetylation status of BubR1 is essential for maintaining the mitotic structure integrity and the control of cell cycle (Choi et al., 2009; Park et al., 2013; Suematsu et al., 2014). …”

Belinostat and vincristine demonstrate mutually synergistic cytotoxicity associated with mitotic arrest and inhibition of polyploidy in a preclinical model of aggressive diffuse large B cell lymphoma

“…Several reports have shown that BubR1 degradation occurs prior to mitotic exit. [39][40][41] The decline in total BubR1 occurs in the similar time frame as the decrease in levels of H3S10Ph.…”

Caspase-3–Dependent Mitotic Checkpoint Inactivation by the Small-Molecule Inducers of Mitotic Slippage SU6656 and Geraldol

“…Cdc20 is an activating cofactor of APC/C during mitosis (8); an active mitotic checkpoint inhibits APC/C through APC/C-dependent polyubiquitylation of Cdc20 and subsequent degradation by the proteasome (12). BubR1 binds to and inhibits both Cdc20 (13) and APC/C itself (14), acting as a pseudosubstrate inhibitor that, depending on acetylation status, can be actively degraded by APC/C Cdc20 (15). The role of Bub3 in the MCC is unclear, although in fission yeast it is involved in MCC localization (16).…”