Repression of CENP-A assembly in metaphase requires HJURP phosphorylation and inhibition by M18BP1

J Cell Biol. 2023 Jun 5;222(6):e202110124. doi: 10.1083/jcb.202110124. Epub 2023 May 4.

Abstract

Centromeres are the foundation for mitotic kinetochore assembly and thus are essential for chromosome segregation. Centromeres are epigenetically defined by nucleosomes containing the histone H3 variant CENP-A. CENP-A nucleosome assembly is uncoupled from replication and occurs in G1, but how cells control this timing is incompletely understood. The formation of CENP-A nucleosomes in vertebrates requires CENP-C and the Mis18 complex which recruit the CENP-A chaperone HJURP to centromeres. Using a cell-free system for centromere assembly in X. laevis egg extracts, we discover two activities that inhibit CENP-A assembly in metaphase. HJURP phosphorylation prevents the interaction between HJURP and CENP-C in metaphase, blocking the delivery of soluble CENP-A to centromeres. Non-phosphorylatable mutants of HJURP constitutively bind CENP-C in metaphase but are not sufficient for new CENP-A assembly. We find that the M18BP1.S subunit of the Mis18 complex also binds to CENP-C to competitively inhibit HJURP's access to centromeres. Removal of these two inhibitory activities causes CENP-A assembly in metaphase.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Autoantigens / metabolism
  • Carrier Proteins* / metabolism
  • Centromere Protein A* / metabolism
  • Centromere* / metabolism
  • DNA-Binding Proteins* / metabolism
  • Metaphase
  • Nucleosomes* / metabolism
  • Phosphorylation
  • Xenopus Proteins* / metabolism
  • Xenopus laevis / genetics

Substances

  • Autoantigens
  • Carrier Proteins
  • Centromere Protein A
  • M18BP1 protein, Xenopus
  • Nucleosomes
  • Xenopus Proteins
  • Holliday junction recognizing protein, Xenopus
  • DNA-Binding Proteins