Abstract:The spindle assembly checkpoint (SAC) maintains genomic integrity by preventing progression of mitotic cell division until all chromosomes are stably attached to spindle microtubules. The SAC critically relies on the paralogues Bub1 and BubR1/Mad3, which integrate kinetochore–spindle attachment status with generation of the anaphase inhibitory complex MCC. We previously reported on the widespread occurrences of independent gene duplications of an ancestral ‘MadBub’ gene in eukaryotic evolution and the striking… Show more
“…Our understanding of the function of BubR1 in the SAC has been greatly facilitated by functional and structural studies on the MCC and of its interaction with APC/C. High-resolution structures of the APC/C MCC complex [ 43 , 46 , 47 ] have offered an ideal framework to understand the molecular basis of the interaction of MCC with the APC/C, including the role of specific BubR1 sequences identified in previous studies [ 71 ], such as the KEN1 and KEN2 boxes and the more recently identified ABBA motifs [ 3 , 39 , 41 , 42 , 43 , 44 , 72 , 73 , 74 , 75 , 76 , 77 ]. The overall picture emerging from these analyses is that a MCC core complex containing one copy each of BubR1, Bub3, Cdc20, and Mad2 binds a second Cdc20 molecule, possibly already bound to the APC/C [ 2 , 44 , 45 , 46 , 47 ].…”
Section: Discussionmentioning
confidence: 99%
“…Bub1 and BubR1 originated through multiple independent gene-duplication events from a precursor (singleton) surmised to be already present in the hypothetical last eukaryotic common ancestor (LECA). Gene duplication invariably led to sub-functionalization of the resulting gene products [ 3 , 4 ] ( Figure 1 A). Figure 1 Kinetochore Localization and Turnover of Long BubR1 Loop Mutants in HeLa Cells (A) Schematic overview of Bub1 and BubR1 domain organization.…”
SummaryThe spindle assembly checkpoint (SAC) prevents premature sister chromatid separation during mitosis. Phosphorylation of unattached kinetochores by the Mps1 kinase promotes recruitment of SAC machinery that catalyzes assembly of the SAC effector mitotic checkpoint complex (MCC). The SAC protein Bub3 is a phospho-amino acid adaptor that forms structurally related stable complexes with functionally distinct paralogs named Bub1 and BubR1. A short motif (“loop”) of Bub1, but not the equivalent loop of BubR1, enhances binding of Bub3 to kinetochore phospho-targets. Here, we asked whether the BubR1 loop directs Bub3 to different phospho-targets. The BubR1 loop is essential for SAC function and cannot be removed or replaced with the Bub1 loop. BubR1 loop mutants bind Bub3 and are normally incorporated in MCC in vitro but have reduced ability to inhibit the MCC target anaphase-promoting complex (APC/C), suggesting that BubR1:Bub3 recognition and inhibition of APC/C requires phosphorylation. Thus, small sequence differences in Bub1 and BubR1 direct Bub3 to different phosphorylated targets in the SAC signaling cascade.
“…Our understanding of the function of BubR1 in the SAC has been greatly facilitated by functional and structural studies on the MCC and of its interaction with APC/C. High-resolution structures of the APC/C MCC complex [ 43 , 46 , 47 ] have offered an ideal framework to understand the molecular basis of the interaction of MCC with the APC/C, including the role of specific BubR1 sequences identified in previous studies [ 71 ], such as the KEN1 and KEN2 boxes and the more recently identified ABBA motifs [ 3 , 39 , 41 , 42 , 43 , 44 , 72 , 73 , 74 , 75 , 76 , 77 ]. The overall picture emerging from these analyses is that a MCC core complex containing one copy each of BubR1, Bub3, Cdc20, and Mad2 binds a second Cdc20 molecule, possibly already bound to the APC/C [ 2 , 44 , 45 , 46 , 47 ].…”
Section: Discussionmentioning
confidence: 99%
“…Bub1 and BubR1 originated through multiple independent gene-duplication events from a precursor (singleton) surmised to be already present in the hypothetical last eukaryotic common ancestor (LECA). Gene duplication invariably led to sub-functionalization of the resulting gene products [ 3 , 4 ] ( Figure 1 A). Figure 1 Kinetochore Localization and Turnover of Long BubR1 Loop Mutants in HeLa Cells (A) Schematic overview of Bub1 and BubR1 domain organization.…”
SummaryThe spindle assembly checkpoint (SAC) prevents premature sister chromatid separation during mitosis. Phosphorylation of unattached kinetochores by the Mps1 kinase promotes recruitment of SAC machinery that catalyzes assembly of the SAC effector mitotic checkpoint complex (MCC). The SAC protein Bub3 is a phospho-amino acid adaptor that forms structurally related stable complexes with functionally distinct paralogs named Bub1 and BubR1. A short motif (“loop”) of Bub1, but not the equivalent loop of BubR1, enhances binding of Bub3 to kinetochore phospho-targets. Here, we asked whether the BubR1 loop directs Bub3 to different phospho-targets. The BubR1 loop is essential for SAC function and cannot be removed or replaced with the Bub1 loop. BubR1 loop mutants bind Bub3 and are normally incorporated in MCC in vitro but have reduced ability to inhibit the MCC target anaphase-promoting complex (APC/C), suggesting that BubR1:Bub3 recognition and inhibition of APC/C requires phosphorylation. Thus, small sequence differences in Bub1 and BubR1 direct Bub3 to different phosphorylated targets in the SAC signaling cascade.
“…•MadBub duplicates diverged into a Bub-like and Mad-like protein through reciprocal domain/motif loss [12,13] Allowing for loss of domains in homology searches, obtaining a high-quality gene tree.…”
Section: Understanding Functional Divergence After Gene Duplicationmentioning
Comparative genomics has proven a fruitful approach to acquire many functional and evolutionary insights into core cellular processes. Here it is argued that in order to perform accurate and interesting comparative genomics, one first and foremost has to be able to recognize, postulate, and revise different evolutionary scenarios. After all, these studies lack a simple protocol, due to different proteins having different evolutionary dynamics and demanding different approaches. The authors here discuss this challenge from a practical (what are the observations?) and conceptual (how do these indicate a specific evolutionary scenario?) viewpoint, with the aim to guide investigators who want to analyze the evolution of their protein(s) of interest. By sharing how the authors draft, test, and update such a scenario and how it directs their investigations, the authors hope to illuminate how to execute molecular evolution studies and how to interpret them. Also see the video abstract here https://youtu.be/VCt3l2pbdbQ.
“…The MCC component BubR1 and the kinase Bub1, which acts as a stable scaffold for coordinating checkpoint signaling (Elowe, 2011;Rischitor et al, 2007), are distant paralogs, produced by duplication and subfunctionalization of an ancestral MadBub gene. Strikingly, duplication has occurred independently in at least 16 different lineages, with most paralogs subject to comparable evolutionary fates (Tromer et al, 2016). The ancestral MadBub had both a kinase domain and a KEN box motif essential for APC/C-Cdc20 inhibition.…”
Section: Genomics-led Advances In Understanding Mitotic Checkpoint Anmentioning
confidence: 99%
“…Phylogenomics can predict previously unknown functional interactions by identifying protein domains and proteins that have similar species distribution, suggesting a degree of co-evolution. This approach led to the identification of a co-evolved unit containing a KEN box flanked by two ABBA motifs in BubR1, which was shown to be essential for APC/C inhibition by the SAC (Tromer et al, 2016). Another phylogenomics study pointed to a possible function of the nucleoporin Y-complex (Loïodice et al, 2004;Zuccolo et al, 2007) in SAC signaling (van Hooff et al, 2017a).…”
Section: Genomics-led Advances In Understanding Mitotic Checkpoint Anmentioning
A long-appreciated variation in fundamental cell biological processes between different species is becoming increasingly tractable due to recent breakthroughs in whole-genome analyses and genome editing techniques. However, the bulk of our mechanistic understanding in cell biology continues to come from just a few well-established models. In this Review, I use the highly diverse strategies of chromosome segregation in eukaryotes as an instrument for a more general discussion on phenotypic variation, possible rules underlying its emergence and its utility in understanding conserved functional relationships underlying this process. Such a comparative approach, supported by modern molecular biology tools, might provide a wider, holistic view of biology that is difficult to achieve when concentrating on a single experimental system.
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