skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.


Title: Differential requirements for the CENP-O complex reveal parallel PLK1 kinetochore recruitment pathways
Similar to other core biological processes, the vast majority of cell division components are essential for viability across human cell lines. However, recent genome-wide screens have identified a number of proteins that exhibit cell line–specific essentiality. Defining the behaviors of these proteins is critical to our understanding of complex biological processes. Here, we harness differential essentiality to reveal the contributions of the four-subunit centromere-localized CENP-O complex, whose precise function has been difficult to define. Our results support a model in which the CENP-O complex and BUB1 act in parallel pathways to recruit a threshold level of PLK1 to mitotic kinetochores, ensuring accurate chromosome segregation. We demonstrate that targeted changes to either pathway sensitizes cells to the loss of the other component, resulting in cell-state dependent requirements. This approach also highlights the advantage of comparing phenotypes across diverse cell lines to define critical functional contributions and behaviors that could be exploited for the targeted treatment of disease.  more » « less
Award ID(s):
2029868
PAR ID:
10233472
Author(s) / Creator(s):
; ;
Editor(s):
Bloom, Kerry
Date Published:
Journal Name:
Molecular Biology of the Cell
Volume:
32
Issue:
8
ISSN:
1059-1524
Page Range / eLocation ID:
712 to 721
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. Bloom, Kerry (Ed.)
    The kinetochore is a macromolecular structure that is needed to ensure proper chromosome segregation during each cellular division. The kinetochore is assembled upon a platform of the 16-subunit constitutive centromere-associated network (CCAN), which is present at centromeres throughout the cell cycle. The nature and regulation of CCAN assembly, interactions, and dynamics needed to facilitate changing centromere properties and requirements remain to be fully elucidated. The CENP-LN complex is a CCAN component that displays unique cell cycle–dependent localization behavior, peaking in the S phase. Here, we demonstrate that phosphorylation of CENP-L and CENP-N controls CENP-LN complex formation and localization in a cell cycle–dependent manner. Mimicking constitutive phosphorylation of either CENP-L or CENP-N or simultaneously preventing phosphorylation of both proteins prevents CENP-LN localization and disrupts chromosome segregation. Our work suggests that cycles of phosphorylation and dephosphorylation are critical for CENP-LN complex recruitment and dynamics at kinetochores to enable cell cycle–dependent CCAN reorganization. 
    more » « less
  2. Centromeres are marked by the centromere-specific histone H3 variant CENP-A/CENH3. Throughout the cell cycle, the constitutive centromere-associated network is bound to CENP-A chromatin, but how this protein network modifies CENP-A nucleosome conformations in vivo is unknown. Here, we purify endogenous centromeric chromatin associated with the CENP-C complex across the cell cycle and analyze the structures by single-molecule imaging and biochemical assays. CENP-C complex–bound chromatin was refractory to MNase digestion. The CENP-C complex increased in height throughout the cell cycle culminating in mitosis, and the smaller CENP-C complex corresponds to the dimensions of in vitro reconstituted constitutive centromere-associated network. In addition, we found two distinct CENP-A nucleosomal configurations; the taller variant was associated with the CENP-C complex. Finally, CENP-A mutants partially corrected CENP-C overexpression–induced centromeric transcription and mitotic defects. In all, our data support a working model in which CENP-C is critical in regulating centromere homeostasis by supporting a unique higher order structure of centromeric chromatin and altering the accessibility of the centromeric chromatin fiber for transcriptional machinery. 
    more » « less
  3. Walczak, Claire E (Ed.)
    Mitotic kinetochores assemble via the hierarchical recruitment of numerous cytosolic components to the centromere region of each chromosome. However, how these orderly and localized interactions are achieved without spurious macromolecular assemblies forming from soluble kinetochore components in the cell cytosol remains poorly understood. We developed assembly assays to monitor the recruitment of GFP-tagged recombinant proteins and native proteins from human cell extracts to inner kinetochore components immobilized on microbeads. In contrast to prior work in yeast and Xenopus egg extracts, we find that human mitotic cell extracts fail to support de novo assembly of microtubule-binding sub-complexes. A subset of interactions, such as those between CENP-A–containing nucleosomes and CENP-C, are permissive under these conditions. However, the subsequent phospho-dependent binding of the Mis12 complex is less efficient, whereas recruitment of the Ndc80 complex is blocked, leading to weak microtubule-binding activity of assembled particles. Using molecular variants of the Ndc80 complex, we show that auto-inhibition of native Ndc80 complex restricts its ability to bind to the CENP-T/W complex, whereas inhibition of the Ndc80 microtubule-binding is driven by a different mechanism. Together, our work reveals regulatory mechanisms that guard against the spurious formation of cytosolic microtubule-binding kinetochore particles. 
    more » « less
  4. All eukaryotic genomes are packaged into basic units of DNA wrapped around histone proteins called nucleosomes. The ability of histones to specify a variety of epigenetic states at defined chromatin domains is essential for cell survival. The most distinctive type of chromatin is found at centromeres, which are marked by the centromere-specific histone H3 variant CENP-A. Many of the factors that regulate CENP-A chromatin have been identified; however, our understanding of the mechanisms of centromeric nucleosome assembly, maintenance, and reorganization remains limited. This review discusses recent insights into these processes and draws parallels between centromeric and noncentromeric chromatin assembly mechanisms. 
    more » « less
  5. Li, Zhiming (Ed.)
    Acetylation of lysine residues is an important and common post-translational regulatory mechanism occurring on thousands of non-histone proteins. Lysine deacetylases (KDACs or HDACs) are a family of enzymes responsible for removing acetylation. To identify the biological mechanisms regulated by individual KDACs, we created HT1080 cell lines containing chromosomal point mutations, which endogenously express either KDAC6 or KDAC8 having single inactivated catalytic domain. Engineered HT1080 cells expressing inactive KDA6 or KDAC8 domains remained viable and exhibited enhanced acetylation on known substrate proteins. RNA-seq analysis revealed that many changes in gene expression were observed when KDACs were inactivated, and that these gene sets differed significantly from knockdown and knockout cell lines. Using GO ontology, we identified several critical biological processes associated specifically with catalytic activity and others attributable to non-catalytic interactions. Treatment of wild-type cells with KDAC-specific inhibitors Tubastatin A and PCI-34051 resulted in gene expression changes distinct from those of the engineered cell lines, validating this approach as a tool for evaluating in-cell inhibitor specificity and identifying off-target effects of KDAC inhibitors. Probing the functions of specific KDAC domains using these cell lines is not equivalent to doing so using previously existing methods and provides novel insight into the catalytic functions of individual KDACs by investigating the molecular and cellular changes upon genetic inactivation. 
    more » « less