The histone γH2A.X is involved in Toxoplasma gondii replication-associated DNA stress

BOGADO SS; DALMASSO MC; VANAGAS L; GANUZA A; FENOY IM; KIM K; SULLIVAN WJ; ANGEL SO

Oxford

Congreso; 12th International Congress on Toxoplasmosis; 2013

Toxoplasma gondii is an apicomplexan parasite with a complex life cycle composed of multiple stages. The tachyzoite stage, which occurs in both definitive and intermediate hosts, is a highly replicative phase that disseminates to almost all tissues and organs. A H2A.X histone was recently described in the parasite that associates with inactive chromatin, and its phosphorylated form (γH2A.X) is present at basal levels even without exogenous DNA damage. H2A.X associates with H2Ba, but not H2Bv (renamed H2B.Z), the partner of H2A.Z. Ectopic expression of T. gondii H2A.X and a mutated version that replaced the C-terminal serine 131 (S131) withalanine, both fused to c- myc epitope (mycH2AX and mycH2AXS131A respectively), showed that the S131 is not required for genome positioning of this histone in silenced chromatin or for dimerization with canonical H2B. However S131 is important for normal parasite replication. This growth impairment increased in the presence of the topoisomerase I inhibitor camptothecin (CPT). The mycH2AX lines exhibited resistance to CPT. We also found that the parasite’s H2A.X is phosphorylated  throughout the cell cycle, mainly during S phase. Our data suggest that the basal γH2A.X in the tachyzoite could be associated with replication-associated DNA stress.