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Intrabody-mediated diverting of HP1β to the cytoplasm induces co-aggregation of H3-H4 histones and lamin-B receptor

Cardinale, A and Filesi, I and Biocca, S and Singh, PB (2015) Intrabody-mediated diverting of HP1β to the cytoplasm induces co-aggregation of H3-H4 histones and lamin-B receptor. Experimental Cell Research, 338 (1). pp. 70-81. ISSN 0014-4827

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Abstract

Diverting a protein from its intracellular location is a unique property of intrabodies. To interfere with the intracellular traffic of heterochromatin protein 1β (HP1β) in living cells, we have generated a cytoplasmic targeted anti-HP1β intrabody, specifically directed against the C-terminal portion of the molecule. HP1β is a conserved component of mouse and human constitutive heterochromatin involved in diverse nuclear functions including gene silencing, DNA repair and nuclear membrane assembly. We found that the anti-HP1β intrabody sequesters HP1β into cytoplasmic aggregates, inhibiting its traffic to the nucleus. Lamin B receptor (LBR) and a subset of core histones (H3/H4) are also specifically co-sequestered in the cytoplasm of anti-HP1β intrabody-expressing cells. Methylated histone H3 at K9 (Me9H3), a marker of constitutive heterochromatin, is not affected by the anti-HP1β intrabody expression. Hyper-acetylating conditions completely dislodge H3 from HP1β:LBR containing aggregates. The expression of anti-HP1β scFv fragments induces apoptosis, associated with an alteration of nuclear morphology. Both these phenotypes are specifically rescued either by overexpression of recombinant full length HP1β or by HP1β mutant containing the chromoshadow domain, but not by recombinant LBR protein. The HP1β-chromodomain mutant, on the other hand, does not rescue the phenotypes, but does compete with LBR for binding to HP1β. These findings provide new insights into the mode of action of cytoplasmic-targeted intrabodies and the interaction between HP1β and its binding partners involved in peripheral heterochromatin organisation.

Item Type: Article
Uncontrolled Keywords: 0601 Biochemistry And Cell Biology, 1103 Clinical Sciences
Subjects: Q Science > QH Natural history > QH301 Biology
Divisions: Natural Sciences and Psychology
Publisher: Elsevier
Date Deposited: 12 Jan 2016 12:25
Last Modified: 07 Sep 2017 10:03
DOI or Identification number: 10.1016/j.yexcr.2015.09.006
URI: http://researchonline.ljmu.ac.uk/id/eprint/2557

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