Toxoplasma gondii H2B.Z histone acetylation is involved in parasite development

VANAGAS, LAURA; MUÑOZ DANIELA; CRISTALDI, CONSTANZA; GANUZA AGUSTINA; SULLIVAN, WILLIAM J.; KAMI KIM; ANGEL, SERGIO O.

Congreso; Molecular parasitology meeting; 2021

T. gondii and other apicomplexan parasites possess an unusual H2B variant called H2B.Z which isfound in nucleosomes containing H2A.Z, another histone variant. H2A.Z and H2B.Z are positionedat transcription start sites (TSS) together with H3K4Me3 and both histone variants are highlyacetylated at their N-terminal tails. We over-expressed myc-tagged H2B.Z in RH strain in whichthe acetylatable lysine residues were maintained (c-Myc-K-OE) or mutated to either the neutralamino acid alanine (c-Myc-A-OE) or the positively charged arginine (c-Myc-R-OE). c-Myc-A-OEand c-Myc-R-OE were used to disrupt the endogenous essential H2B.Z gene using CRISPR/Cas9.c-Myc-R/KO presented a lower growth rate and an increment in bradyzoite differentiation ratecompared to the parental in vitro. Infection of C57BL/6 mice with 100 ? 10,000 c-Myc-R/KOtachyzoites showed no virulence, but elicited the expected immune response, and did notdevelop brain cysts. Mice previously infected with c-Myc-R/KO were protected from parental RHstrain infection. ChIP-qPCR with anti-c-Myc and ?H2A.Z antibodies showed that neither H2B.Znor H2A.Z were enriched in promoters of active and silent genes, in c-Myc-R/KO. c-Myc-A/KO didnot show any phenotypical change in vitro and a modest delay in killing infected mice. Thesefindings suggest that regulation of positive lysine charge of the N-terminal region of H2B.Z isrelevant for the genome localization, which would regulate gene expression and, as aconsequence would be important in the control of parasite development and survival duringanimal infection.