TPEN, a Zn2+/Fe2+ chelator with low affinity for Ca2+, inhibits lamin assembly, destabilizes nuclear architecture and may independently protect nuclei from apoptosis in vitro

We used Xenopus egg extracts to examine the effects of TPEN, a chelator with strong affinities for Zn2+, Fe2+, and Mn2+, on nuclear assembly in vitro. At concentrations above 1 mM, TPEN blocked the assembly of the nuclear lamina and produced nuclei that were profoundly sensitive to stress-induced ba...

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Bibliographic Details
Published in:Cell calcium (Edinburgh) 1998-02, Vol.23 (2-3), p.151-164
Main Authors: Shumaker, D K, Vann, L R, Goldberg, M W, Allen, T D, Wilson, K L
Format: Article
Language:English
Subjects:
Animals
Apoptosis
Calcium - metabolism
Calcium - pharmacology
Cell Nucleus - drug effects
Cell Nucleus - metabolism
Cell Nucleus - ultrastructure
Chelating Agents - metabolism
DNA Replication - drug effects
Egtazic Acid - analogs & derivatives
Egtazic Acid - pharmacology
Ethylenediamines - metabolism
Ethylenediamines - pharmacology
Ferrous Compounds - metabolism
Ferrous Compounds - pharmacology
Lamins
Nuclear Proteins - metabolism
Xenopus
Zinc - metabolism
Zinc - pharmacology
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Summary:We used Xenopus egg extracts to examine the effects of TPEN, a chelator with strong affinities for Zn2+, Fe2+, and Mn2+, on nuclear assembly in vitro. At concentrations above 1 mM, TPEN blocked the assembly of the nuclear lamina and produced nuclei that were profoundly sensitive to stress-induced balloon-like 'shedding' of nuclear membranes away from chromatin-associated membranes. TPEN-arrested nuclei were also defective for DNA replication, which could be explained as secondary to the lack of a lamina. Imaging of TPEN-arrested nuclei by field emission in-lens scanning electron microscopy (FEISEM) revealed clustered, structurally-perturbed nuclear pore complexes. TPEN-arrested nuclei were defective in the accumulation of fluorescent karyophilic proteins. All detectable effects caused by TPEN were downstream of the effects of BAPTA, a Ca2+/Zn2+ chelator that blocks pore complex assembly at two distinct early stages. Surprisingly, TPEN-arrested nuclei, but not control nuclei, remained active for replication in apoptotic extracts, as assayed by [32P]-dCTP incorporation into high molecular weight DNA, suggesting that TPEN blocks a metal-binding protein(s) required for nuclear destruction during programmed cell death.
ISSN:0143-4160
DOI:10.1016/S0143-4160(98)90114-2