Abstract
Centromeres are unique chromosomal loci that promote the assembly of kinetochores, macromolecular complexes that bind spindle microtubules during mitosis. In most organisms, centromeres lack defined genetic features. Rather, they are specified epigenetically by a centromere-specific histone H3 variant, CENP-A. The Mis18 complex, comprising the Mis18α:Mis18β subcomplex and M18BP1, is crucial for CENP-A homeostasis. It recruits the CENP-A-specific chaperone HJURP to centromeres and primes it for CENP-A loading. We report here that a specific arrangement of Yippee domains in a human Mis18α:Mis18β 4:2 hexamer binds two copies of M18BP1 through M18BP1's 140 N-terminal residues. Phosphorylation by Cyclin-dependent kinase 1 (CDK1) at two conserved sites in this region destabilizes binding to Mis18α:Mis18β, limiting complex formation to the G1 phase of the cell cycle. Using an improved viral 2A peptide co-expression strategy, we demonstrate that CDK1 controls Mis18 complex recruitment to centromeres by regulating oligomerization of M18BP1 through the Mis18α:Mis18β scaffold.
Highlights
In all eukaryotes, faithful chromosome duplication and segregation to the daughter cells is essential for cell viability and development
We performed pull-down assays with M18BP1 fragments that had been previously phosphorylated with recombinant human Cyclin-dependent kinase 1 (CDK1):Cyclin B1
Previous studies suggested that CDK1 activity regulates CENP-A incorporation into centromeres (McKinley and Cheeseman, 2014; Silva et al, 2012) and that part of this regulation is through phosphorylation of M18BP1, which prevents complex formation with Mis18a:Mis18b (McKinley and Cheeseman, 2014)
Summary
Faithful chromosome duplication and segregation to the daughter cells is essential for cell viability and development. Chromosomes attach to spindle microtubules through large multisubunit assemblies known as kinetochores (Pesenti et al, 2016). Kinetochores harness a poorly understood molecular mechanism of ‘error correction’ that leads to selective stabilization of bi-oriented attachments (Foley and Kapoor, 2013). Kinetochores assemble on centromeres, unique chromosomal loci characterized by a strong enrichment of the histone H3 variant centromere protein A (CENP-A) (Earnshaw and Rothfield, 1985). Centromeres in different organisms often consist of long arrays of repetitive sequences, such as the human 171-basepair a-satellite repeats (Fukagawa and Earnshaw, 2014; McKinley and Cheeseman, 2016). There are instances in humans and other species of neo-centromeres that become established on non-repetitive sequences
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