Affiliation:
1. Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, Indiana 46202
2. Department of Genetics, University of Georgia, Athens, Georgia 30602
Abstract
ABSTRACT
GCN5 is a histone acetyltransferase (HAT) essential for development in mammals and critical to stress responses in yeast. The protozoan parasite
Toxoplasma gondii
is a serious opportunistic pathogen. The study of epigenetics and gene expression in this ancient eukaryote has pharmacological relevance and may facilitate the understanding of these processes in higher eukaryotes. Here we show that the disruption of
T. gondii
GCN5 yields viable parasites, which were subsequently employed in a proteomics study to identify gene products affected by its loss. Promoter analysis of these TgGCN5-dependent genes, which were mostly parasite specific, reveals a conserved T-rich element. The loss of TgGCN5 does not attenuate virulence in an in vivo mouse model. We also discovered that
T. gondii
is the only invertebrate reported to date possessing a second GCN5 (TgGCN5-B). TgGCN5-B harbors a strikingly divergent N-terminal domain required for nuclear localization. Despite high homology between the HAT domains, the two TgGCN5s exhibit differing substrate specificities. In contrast to TgGCN5-A, which exclusively targets lysine 18 of H3, TgGCN5-B acetylates multiple lysines in the H3 tail. We also identify two ADA2 homologues that interact differently with the TgGCN5s. TgGCN5-B has the potential to compensate for TgGCN5-A, which probably arose from a gene duplication unique to
T. gondii
. Our work reveals an unexpected complexity in the GCN5 machinery of this primitive eukaryote.
Publisher
American Society for Microbiology
Subject
Molecular Biology,General Medicine,Microbiology
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5. Lytic Cycle of
Toxoplasma gondii
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