Mechanism of centromere recruitment of the CENP-A chaperone HJURP and its implications for centromere licensing

Dongqing Pan,Andrea Musacchio,Annika Take,Kai Walstein,Nadine Kaiser,David Bier

doi:10.1038/s41467-019-12019-6

Dongqing Pan, Andrea Musacchio + Show 4 more

Open Access

https://doi.org/10.1038/s41467-019-12019-6

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Abstract

Nucleosomes containing the histone H3 variant CENP-A are the epigenetic mark of centromeres, the kinetochore assembly sites required for chromosome segregation. HJURP is the CENP-A chaperone, which associates with Mis18α, Mis18β, and M18BP1 to target centromeres and deposit new CENP-A. How these proteins interact to promote CENP-A deposition remains poorly understood. Here we show that two repeats in human HJURP proposed to be functionally distinct are in fact interchangeable and bind concomitantly to the 4:2:2 Mis18α:Mis18β:M18BP1 complex without dissociating it. HJURP binds CENP-A:H4 dimers, and therefore assembly of CENP-A:H4 tetramers must be performed by two Mis18αβ:M18BP1:HJURP complexes, or by the same complex in consecutive rounds. The Mis18α N-terminal tails blockade two identical HJURP-repeat binding sites near the Mis18αβ C-terminal helices. These were identified by photo-cross-linking experiments and mutated to separate Mis18 from HJURP centromere recruitment. Our results identify molecular underpinnings of eukaryotic chromosome inheritance and shed light on how centromeres license CENP-A deposition.

Highlights

Nucleosomes containing the histone H3 variant CENP-A are the epigenetic mark of centromeres, the kinetochore assembly sites required for chromosome segregation
CENP-A is the epigenetic marker of centromeres, and dissecting the molecular basis of its deposition and maintenance through subsequent cell divisions is expected to clarify the foundations of centromere inheritance
A successful molecular model of CENPA deposition ought to include answers to several crucial questions, including: (1) why is the deposition reaction limited to the existing CENP-A domain? (2) Does the deposition reaction target for eviction and replacement a specific neighboring nucleosome, e.g., an H3 nucleosome marked by particular interactions with neighboring CENP-A nucleosome(s)? And (3) what limits the deposition reaction so that the levels of newly deposited CENP-A match the levels of already existing CENP-A, ensuring that the amounts of CENP-A are maintained through the generations?

Summary

Introduction

Nucleosomes containing the histone H3 variant CENP-A are the epigenetic mark of centromeres, the kinetochore assembly sites required for chromosome segregation. HJURP is the CENP-A chaperone, which associates with Mis18α, Mis18β, and M18BP1 to target centromeres and deposit new CENP-A. The Mis18α N-terminal tails blockade two identical HJURP-repeat binding sites near the Mis18αβ C-terminal helices These were identified by photo-cross-linking experiments and mutated to separate Mis[18] from HJURP centromere recruitment. With the exception of a handful of organisms, the enrichment of CENP-A within the centromeric domain appears to be independent of specific DNA sequences[2,3,4,5] This observation is the basis of the concept that centromere identity, which exquisitely depends on CENP-A, is inherited epigenetically. This has shifted the focus onto the mechanisms that allow the centromeric levels of CENP-A to be maintained through cell division, leading to the pioneering discovery of factors involved in new CENP-A deposition[11,12,13,14]

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