Cell News 01/2017
12
Nuclear pore complex formation:
step-wise assembly of a transport gate
Wolfram Antonin
(in alphabetical order)
ABSTRACTS CHAIRS AND SPEAKERS
Institute of Biochemistry and Molecular Cell Biology,
RWTH Aachen University
Nuclear pore complexes are the gatekeepers of the nucleus.
They exclude most macromolecules but mediate the selective
and regulated transport of nuclear proteins and nucleic acids
across the barrier of the nuclear envelope. Having a mass of
approximately 125 MDa, nuclear pore complexes are the larg-
est protein complexes in most vertebrate cells. Despite their
enormous size they are only composed of about 30 different
proteins called nucleoporins. Because of the eight-fold symme-
try of the pore, 8, 16 or even more copies of each nucleoporin
are present per nuclear pore complex. The stepwise coordi-
nated assembly of these huge complexes from more than five
hundred individual components and their integration into the
nuclear envelope is a fascinating example of molecular self-or-
ganisation in cells.
Using a combination of biochemical and cell biological ex-
periments we dissect the molecular mechanisms of nuclear
pore complex assembly. I will present recent progress in our
understanding of how nuclear pore complexes embed into the
two membranes of the nuclear envelope and form a transport
competent pore.
Structure and function of the nuclear pore complex
Bernhard Hampoelz, Andre Schwarz and Martin Beck
European Molecular Biology Laboratory, Heidelberg
Nuclear pore complexes (NPCs) span the nuclear envelope (NE)
and mediate nucleocytoplasmic transport. In metazoan oocytes
and early embryos, NPCs reside not only within the NE, but
also at some endoplasmic reticulum (ER) membrane sheets,
termed annulate lamellae (AL). Although a role for AL as NPC
storage pools has been discussed, it remains controversial
whether and how they contribute to the NPC density at the
NE. Here, we show that AL insert into the NE as the ER feeds
rapid nuclear expansion in Drosophila blastoderm embryos.
We demonstrate that NPCs within AL resemble pore scaffolds
that mature only upon insertion into the NE. We delineate
a topological model in which NE openings are critical for AL
uptake that nevertheless occurs without compromising the
permeability barrier of the NE. We finally show that this unan-
ticipated mode of pore insertion is developmentally regulated
and operates prior to gastrulation.
