HP1α targets the chromosomal passenger complex for activation at heterochromatin before mitotic entry.

Jan G Ruppert,Shinya Ohta,William C Earnshaw,Hiroshi Kimura,A Arockia Jeyaprakash,Oscar Molina,Kumiko Samejima,Melpomeni Platani

doi:10.15252/embj.201797677

Jan G Ruppert, Shinya Ohta + Show 6 more

Open Access

https://doi.org/10.15252/embj.201797677

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Abstract

The chromosomal passenger complex (CPC) is directed to centromeres during mitosis via binding to H3T3ph and Sgo1. Whether and how heterochromatin protein 1α (HP1α) influences CPC localisation and function during mitotic entry is less clear. Here, we alter HP1α dynamics by fusing it to a CENP‐B DNA‐binding domain. Tethered HP1 strongly recruits the CPC, destabilising kinetochore–microtubule interactions and activating the spindle assembly checkpoint. During mitotic exit, the tethered HP1 traps active CPC at centromeres. These HP1‐CPC clusters remain catalytically active throughout the subsequent cell cycle. We also detect interactions between endogenous HP1 and the CPC during G2. HP1α and HP1γ cooperate to recruit the CPC to active foci in a CDK1‐independent process. Live cell tracking with Fab fragments reveals that H3S10ph appears well before H3T3 is phosphorylated by Haspin kinase. Our results suggest that HP1 may concentrate and activate the CPC at centromeric heterochromatin in G2 before Aurora B‐mediated phosphorylation of H3S10 releases HP1 from chromatin and allows pathways dependent on H3T3ph and Sgo1 to redirect the CPC to mitotic centromeres.

Highlights

The chromosomal passenger complex (CPC) is a key regulatory factor that controls chromosome segregation during mitosis
Flow cytometry analysis revealed that this resulted in a decrease of the mitotic index to a level similar to that of control cells expressing CB-EY-HP1aW174A and untransfected cells. These results indicate that heterochromatin protein 1a (HP1a) tethering using the CENP-B DNA-binding domain (DBD) results in a phenotype similar to that seen following CENP-B tethering of the core CPC protein INCENP, including metaphase delay, spindle assembly checkpoint (SAC) activation, impaired microtubule attachments to
CPC functions during mitosis are widely studied, but much less is known about CPC activation in G2 phase, when Aurora B activity is first detected

Summary

Introduction

The chromosomal passenger complex (CPC) is a key regulatory factor that controls chromosome segregation during mitosis. The CPC regulates chromosome condensation, release of erroneous kinetochore–microtubule attachments, spindle assembly checkpoint (SAC) activation and cytokinesis [reviewed by (Carmena et al, 2012; van der Waal et al, 2012)]. A defining feature of the CPC is that it functions at different locations at different times during mitosis (Earnshaw & Bernat, 1991). The CPC localises to centromeres in order to regulate chromosomal attachments to the mitotic spindle. A breakthrough came following the discovery of H3T3 phosphorylation by Haspin kinase (Dai et al, 2005) when it was realised that CPC localisation to mitotic centromeres involves survivin binding to H3T3ph (Kelly et al, 2010; Wang et al, 2010). Sgo targeting to H2AT120ph (a product of Bub kinase activity) provides a second mechanism for CPC targeting, with Haspin/H3T3ph localising the CPC to inner centromeres and Bub1/H2AT120ph localising it to kinetochores (Yamagishi et al, 2010)

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