HIPK2 Controls Cytokinesis through Histone H2B Phosphorylation at the Midbody
Author(s)
Moncada, Alice
Date Issued
April 12, 2012
Type
Doctoral Thesis
Abstract
HIPK2 is a multi-talented S/T kinase playing critical role in cell fate decision
during development and in response to genotoxic damage. Here we show that
HIPK2, together with its novel phosphorylation target H2B, is critically involved in
the final steps of cytokinesis and its inactivation promotes tetra- and
polyploidization. Starting from a mass–spec-based identification of H2B as HIPK2
interacting protein, we demonstrated that HIPK2 binds and phosphorylates H2B at
S14 and both proteins localize at the midbody during cytokinesis. The midbody
localization of HIPK2 and H2B-S14P is independent of the presence of chromatin
in the cleavage plane, indicating a distinct role from the DDR activities of both
HIPK2 and H2B proteins. Microscopic studies and live-cell imaging with HIPK2-
proficient and -defective cells revealed that HIPK2 is not necessary for the midbody
localization of H2B but is required for its S14 phosphorylation in this subcellular
compartment. Furthermore, we discovered that HIPK2-deficiency prevents cell
cleavage, leading to regression of the cleavage furrow and accumulation of bi- and
multi-nucleated cells; alternatively, it causes persistence of the connections between
daughter cells with the formation of LIBs and syncytia-like structures, supporting a
main role of HIPK2 in abscission. We rescued all the observed cytokinesis defects
by restoring wild-type HIPK2 expression in Hipk2-/- MEFs and, most strikingly, by
expressing a phosphomimetic H2B-S14D derivative, thus showing that H2B-S14P
is required for a faithful cytokinesis. Overall, our data point at the HIPK2/H2B
interplay as an important regulator of the final step of cell division and uncover a
novel HIPK2 function in the prevention of tetraploid cell formation.
Additional information
Dottorato di ricerca in Genetica e biologia cellulare
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