CDK1-mediated phosphorylation at H2B serine 6 is required for mitotic chromosome segregation.

Markus Seibert,Johan A Slotman,Michael Kracht,John R Daum,Onur Sen,Ralf Jacob,Nikolaus A Watson,M Lienhard Schmitz,Thomas Braun,Marcus Krüger,Gary J Gorbsky,Jonathan M.G Higgins,Adriaan B Houtsmuller

doi:10.1083/jcb.201806057

Abstract

Faithful mitotic chromosome segregation is required for the maintenance of genomic stability. We discovered the phosphorylation of histone H2B at serine 6 (H2B S6ph) as a new chromatin modification site and found that this modification occurs during the early mitotic phases at inner centromeres and pericentromeric heterochromatin. This modification is directly mediated by cyclin B1-associated CDK1, and indirectly by Aurora B, and is antagonized by PP1-mediated dephosphorylation. H2B S6ph impairs chromatin binding of the histone chaperone SET (I2PP2A), which is important for mitotic fidelity. Injection of phosphorylation-specific H2B S6 antibodies in mitotic cells caused anaphase defects with impaired chromosome segregation and incomplete cytokinesis. As H2B S6ph is important for faithful chromosome separation, this modification may contribute to the prevention chromosomal instability and aneuploidy which frequently occur in cancer cells.

Highlights

The precise temporal and spatial control of events during cell cycle progression depends on many enzymatic activities
We discovered the phosphorylation of histone H2B at serine 6 (H2B S6ph) as a new chromatin modification site and found that this modification occurs during the early mitotic phases at inner centromeres and pericentromeric heterochromatin
H2B S6ph occurs in early mitosis During a search for new histone phosphorylation sites by mass spectrometry (MS), we discovered modification of H2B S6 by in vitro kinase assays

Summary

Introduction

The precise temporal and spatial control of events during cell cycle progression depends on many enzymatic activities This is well exemplified by the process of mitosis, which is characterized by a widespread increase in phosphorylation site occupancy, as revealed by quantitative phosphoproteomics (Olsen et al, 2010). Kinases controlling mitosis include the master regulator CDK1-cyclin B1, which phosphorylates multiple substrates, including linker histone H1, and is indispensable for early mitotic events (Langan et al, 1989; Domingo-Sananes et al, 2011). Another important mitotic kinase is Aurora B which, together with INCENP, Borealin, and Survivin, forms the chromosomal passenger complex (CPC). Mitotic phosphorylation of H3 T3 and H3.3 S31 is enriched at inner centromeres, the chromatin regions between the kinetochore-bound centromeres that are enriched in di- and trimethylated H3 lysine 9 (H3 K9me2/3; Goto et al, 2002; Dai et al, 2005; Hake et al, 2005; Yamagishi et al, 2010; Müller and Almouzni, 2017)

Methods

Results

Conclusion