face cryo-ET density, accounting for ~23 MDa
of structured mass. The more flexibly attached
regions of the CF nups that are not captured by
the current subtomogram-averaged cryo-ET
map account for an additional ~19 MDa of mass.
In addition to these flexibly attached struc-
tured domains, NUP358, NUP214, NUP98, and
NUP42 contain extended FG-repeat regions
emanating from various anchor points at the
outer ring. The degree to which these regions
contribute to the architectural integrity of
the human NPC, as has been shown for the
S. cerevisiaeNPC ( 99 ), and the NPC’sdiffusion
barrier remain important questions for future
research.
We found that the interactions between the
C. thermophilumCF nups and the CNC are
modulated by the small molecule IP 6 , thepresence of which is required for mRNA ex-
port. Future studies are needed to address
the concerted role of posttranslational mod-
ifications, second messengers and other small
molecules, and macromolecular factors in
regulating the assembly and functions of the
NPC cytoplasmic face in mRNA export.
The integral membrane proteins and nu-
clear basket portions of the NPC represent anBleyet al., Science 376 , eabm9129 (2022) 10 June 2022 15 of 18
Fig. 8. Architecture of the
human NPC cytoplasmic
face.Near-atomic composite
structure of the human
NPC generated by docking
individual nup and nup
complex crystal and cryo-EM
structures into a ~12-Å
cryo-ET map of the intact
human NPC, viewed from
(A) the cytoplasmic face
and (B) the central
transport channel as a
cross section. Newly placed
structures include the quanti-
tatively docked NUP358NTD
and the manually docked
NUP88NTD•NUP98APD,
NUP214NTD•DDX19,
GLE1CTD•NUP42GBM, ELYSNTD,
and a CFNC-hub model.
The nuclear envelope is
rendered as a gray isosurface.
Nups are shown in cartoon
representation and colored
according to the legend.
RESEARCH | STRUCTURE OF THE NUCLEAR PORE