posted on 2018-01-19, 00:00authored byPatrick
D. Ellis Fisher, Qi Shen, Bernice Akpinar, Luke K. Davis, Kenny Kwok Hin Chung, David Baddeley, Anđela Šarić, Thomas J. Melia, Bart W. Hoogenboom, Chenxiang Lin, C. Patrick Lusk
Nuclear
pore complexes (NPCs) form gateways that control molecular
exchange between the nucleus and the cytoplasm. They impose a diffusion
barrier to macromolecules and enable the selective transport of nuclear
transport receptors with bound cargo. The underlying mechanisms that
establish these permeability properties remain to be fully elucidated
but require unstructured nuclear pore proteins rich in Phe-Gly (FG)-repeat
domains of different types, such as FxFG and GLFG. While physical
modeling and in vitro approaches have provided a
framework for explaining how the FG network contributes to the barrier
and transport properties of the NPC, it remains unknown whether the
number and/or the spatial positioning of different FG-domains along
a cylindrical, ∼40 nm diameter transport channel contributes
to their collective properties and function. To begin to answer these
questions, we have used DNA origami to build a cylinder that mimics
the dimensions of the central transport channel and can house a specified
number of FG-domains at specific positions with easily tunable design
parameters, such as grafting density and topology. We find the overall
morphology of the FG-domain assemblies to be dependent on their chemical
composition, determined by the type and density of FG-repeat, and
on their architectural confinement provided by the DNA cylinder, largely
consistent with here presented molecular dynamics simulations based
on a coarse-grained polymer model. In addition, high-speed atomic
force microscopy reveals local and reversible FG-domain condensation
that transiently occludes the lumen of the DNA central channel mimics,
suggestive of how the NPC might establish its permeability properties.