Format

Send to

Choose Destination
J Cell Sci. 2019 May 15;132(10). pii: jcs225524. doi: 10.1242/jcs.225524.

Homeostasis of soluble proteins and the proteasome post nuclear envelope reformation in mitosis.

Author information

1
Department of Cell and Chemical Biology, Oncode Institute, Leiden University Medical Center LUMC, Leiden, The Netherlands.
2
Department of Cell and Chemical Biology, Oncode Institute, Leiden University Medical Center LUMC, Leiden, The Netherlands j.j.c.neefjes@lumc.nl.

Abstract

Upon nuclear envelope (NE) fragmentation in the prometaphase, the nuclear and cytosolic proteomes mix and must be redefined to reinstate homeostasis. Here, by using a molecular GFP ladder, we show that in early mitosis, condensed chromatin excludes cytosolic proteins. When the NE reforms tightly around condensed chromatin in late mitosis, large GFP multimers are automatically excluded from the nucleus. This can be circumvented by limiting DNA condensation with Q15, a condensin II inhibitor. Soluble small and other nuclear localization sequence (NLS)-targeted proteins then swiftly enter the expanding nuclear space. We then examined proteasomes, which are located in the cytoplasm and nucleus. A significant fraction of 20S proteasomes is imported by the importin IPO5 within 20 min of reformation of the nucleus, after which import comes to an abrupt halt. This suggests that maintaining the nuclear-cytosol distribution after mitosis requires chromatin condensation to exclude cytosolic material from the nuclear space, and specialized machineries for nuclear import of large protein complexes, such as the proteasome.

KEYWORDS:

Chromatin; IPO5; Mitosis; Nuclear envelope; Nuclear import; Proteasome

PMID:
30992344
DOI:
10.1242/jcs.225524
Free full text

Conflict of interest statement

Competing interestsThe authors declare no competing or financial interests.

Supplemental Content

Full text links

Icon for HighWire
Loading ...
Support Center