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Epichromatin is conserved in Toxoplasma gondii and labels the exterior parasite chromatin throughout the cell cycle

Published online by Cambridge University Press:  23 May 2013

LAURA VANAGAS
Affiliation:
Laboratorio de Parasitología Molecular, IIB-INTECH, CONICET-UNSAM, Av. Intendente Marino Km. 8·2, C.C 164, (B7130IIWA), Chascomús, Prov. Buenos Aires, Argentina
MARIA C. DALMASSO
Affiliation:
Laboratorio de Parasitología Molecular, IIB-INTECH, CONICET-UNSAM, Av. Intendente Marino Km. 8·2, C.C 164, (B7130IIWA), Chascomús, Prov. Buenos Aires, Argentina
JEAN F. DUBREMETZ
Affiliation:
UMR5539 CNRS, Université de Montpellier II, Montpellier, France
ENRIQUE L. PORTIANSKY
Affiliation:
Laboratorio de Análisis de Imágenes, Facultad de Ciencias Veterinarias, Universidad Nacional de La Plata, La Plata, Argentina
DONALD E. OLINS
Affiliation:
Department of Pharmaceutical Sciences, College of Pharmacy, University of New England, Portland, ME, USA
SERGIO O. ANGEL*
Affiliation:
Laboratorio de Parasitología Molecular, IIB-INTECH, CONICET-UNSAM, Av. Intendente Marino Km. 8·2, C.C 164, (B7130IIWA), Chascomús, Prov. Buenos Aires, Argentina
*
*Corresponding author. Laboratorio de Parasitología Molecular, IIB-INTECH, CONICET-UNSAM, Av. Intendente Marino Km. 8·2, C.C 164, (B7130IIWA), Chascomús, Prov. Buenos Aires, Argentina. E-mail: [email protected]

Summary

Toxoplasma gondii is an apicomplexan intracellular protozoan parasite responsible for toxoplasmosis, a disease with considerable medical and economic impact worldwide. Toxoplasma gondii cells never lose the nuclear envelope and their chromosomes do not condense. Here, we tested the murine monoclonal antibody PL2-6, which labels epichromatin (a conformational chromatin epitope based on histones H2A and H2B complexed with DNA), in T. gondii cultured in human fibroblasts. This epitope is present at the exterior chromatin surface of interphase nuclei and on the periphery of mitotic chromosomes in higher eukaryotes. PL2-6 reacted with T. gondii H2A and H2B histones in Western blot (WB) assays. In addition, the antibody reacted with the nuclear fraction of tachyzoites, as a single band coincident with H2B histone. In the T. gondii tachyzoite stage, PL2-6 also had peripheral nuclear localization, as observed by epifluorescence/confocal microscopy and immunoelectron microscopy. Confocal analysis showed that epichromatin is slightly polarized to one face of the parasite exterior chromatin surface. In replicating tachyzoites, PL2-6 also labels the exterior chromatin surface, covering the face of both segregating nuclei, facing the plasma membrane of the mother cell. The possible role of epichromatin in T. gondii is discussed.

Type
Research Article
Copyright
Copyright © Cambridge University Press 2013 

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