Toxoplasma gondii histone H2Bv interacts with H2A.Z but not with H2A.X

DALMASSO, MC; ANGEL, SO

Montana - Estados Unidos

Congreso; Ninth International Congress of Toxoplasmosis.; 2007

One major contributor to gene expression management, DNA replication and repair is chromatin. It is primarily composed of nucleosomes, which serve as spools to wrap and fold DNA in ways that are generally repressive to transcription. Nucleosomes are comprised of core histones (two paired dimers of H2A/H2B and H3/H4) and a linker histone H1, which facilitates the formation of higher-order chromatin structures. Previously, we observed that Toxoplasma gondii expresses two H2Bs: the canonic TgH2Ba and the variant TgH2Bv. Here, we identified three Toxoplasma gondii H2As members based on sequence analysis: TgH2A1 and the variants TgH2AX and TgH2AZ. Semi-quantitative RT-PCR between tachyzoites and bradyzoites was performed to analyze their expression profiles. In contrast to TgH2Bv, TgH2AX and TgH2AZ, canonical TgH2A.1 and TgH2Ba histones presented a cell cycle associated-expression. Histones purified from tachyzoites were analyzed by Western blot and it was observed that TgH2AZ is the less abundant H2A in T. gondii. Finally, the interaction of these histones with the novel TgH2Bv was assessed by co-immunoprecipitations assays. They revealed that TgH2Bv interacts mainly with TgH2AZ. And TgH2AX did not co-immunoprecipitate with TgH2AZ. This data strongly suggest that TgH2AX is absent in the nucleosomes where the dimmer TgH2Bv-TgH2AZ is present.