Phosphorylation in the accessory domain of yeast histone
chaperone protein 1 exposes the nuclear export signal sequence
Sho Ashida1†, Rikuri Morita2†,
Yasuteru Shigeta2, and Ryuhei
Harada2*
1College of Biological Sciences, University of
Tsukuba, Tsukuba, Ibaraki 305-0821, Japan
2Center for Computational Sciences, University of
Tsukuba, Tsukuba, Ibaraki 305-8577, Japan
† These authors contributed equally to this work.
*Correspondence: Ryuhei Harada, Center for
Computational Sciences, University of Tsukuba,
1-1-1 Tennodai, Tsukuba, Ibaraki 305-8577, Japan.
E-mail:ryuhei@ccs.tsukuba.ac.jp
A short running title: Phosphorylation effect on yNap1
Keywords: Histone chaperone, Phosphorylation, Molecular
dynamics, Nuclear export signal/sequence
Total number of manuscript pages: 17 (including References
section)
Number of figures: 4
Number of supplementary figures: 1
Abstract
Histone chaperone proteins assist in the formation of the histone
octamers, the scaffold proteins that facilitate the packing of DNA into
nucleosomes in the cell nucleus. One such histone chaperone protein is
yeast nucleosome assembly protein 1 (yNap1), the crystal structure of
which has been determined and found to have a nuclear export signal
(NES) sequence within its long α-helix. Experimental evidence obtained
from mutagenesis studies of the budding yeast suggests that the NES is
necessary for the transport of yNap1 from the cell nucleus to the
cytosol. However, the NES sequence is masked by an accessory domain, the
exact role of which has not yet been elucidated, especially in
nucleocytoplasmic transport. To clarify the role of the accessory
domain, we focused on its phosphorylation because proteomic experiments
have identified multiple phosphorylation sites on yNap1. To study this
phenomenon computationally, all-atom molecular dynamics simulations of
the non-phosphorylated yNap1 (Nap1-nonP) and phosphorylated yNap1
(Nap1-P) systems were performed. Specifically, we addressed how the NES
sequence is exposed to the protein surface by measuring its
solvent-accessible surface area (SASA). It was found that the median of
the SASA distribution of Nap1-P was greater than that of Nap1-nonP,
indicating that phosphorylation in the accessory domain exposes the NES,
resulting in its increased accessibility. In conclusion, yNap1 might
modulate the accessibility of the NES by dislocating the accessory
domain through its phosphorylation.