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Mol Biol Cell. 2016 Dec 15;27(25):3964-3971. Epub 2016 Oct 26.

Dissecting Torsin/cofactor function at the nuclear envelope: a genetic study.

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Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520.
Department of Cell Biology, Yale School of Medicine, New Haven, CT 06520.
Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520


The human genome encodes four Torsin ATPases, the functions of which are poorly understood. In this study, we use CRISPR/Cas9 engineering to delete all four Torsin ATPases individually and in combination. Using nuclear envelope (NE) blebbing as a phenotypic measure, we establish a direct correlation between the number of inactivated Torsin alleles and the occurrence of omega-shaped herniations within the lumen of the NE. A similar, although not identical, redundancy is observed for LAP1 and LULL1, which serve as regulatory cofactors for a subset of Torsin ATPases. Unexpectedly, deletion of Tor2A in a TorA/B/3A-deficient background results in a stark increase of bleb formation, even though Tor2A does not respond to LAP1/LULL1 stimulation. The robustness of the observed phenotype in Torsin-deficient cells enables a structural analysis via electron microscopy tomography and a compositional analysis via immunogold labeling. Ubiquitin and nucleoporins were identified as distinctively localizing components of the omega-shaped bleb structure. These findings suggest a functional link between the Torsin/cofactor system and NE/nuclear pore complex biogenesis or homeostasis and establish a Torsin-deficient cell line as a valuable experimental platform with which to decipher Torsin function.

[Available on 2017-03-02]
[Indexed for MEDLINE]
Free PMC Article

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