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GCN5a is a telomeric lysine acetyltransferase whose loss primes Toxoplasma gondii for latency (RNAseq)

ABSTRACT: Toxoplasma gondii is a protozoan parasite that causes persistent infection in warm-blooded vertebrates by undergoing differentiation from a replicative stage (tachyzoites) to a latent encysted stage (bradyzoites). Stage differentiation is critical for transmission and pathogenesis and relies on gene regulation driven by a network of transcription and epigenetic factors. We previously found in non-cystogenic type I RH strain parasites that the lysine acetyltransferase (KAT), GCN5a, is dispensable in tachyzoites but required to upregulate stress-response genes, suggesting a link with bradyzoite conversion. To address this possibility, we generated endogenously tagged GCN5a parasites and a genetic knockout in cystogenic type II Pru strain. We show that GCN5a protein, but not mRNA, increases during differentiation and complexes with unique protein partners, most of which contain AP2 domains. Pru strain tachyzoites lacking GCN5a augment bradyzoite-specific gene expression in the absence of stress. Loss of GCN5a slowed tachyzoite replication and heightened sensitivity to bradyzoite conversion but resulted in smaller cyst sizes compared to wildtype. Using CUT&Tag, we delineated the chromosomal occupancy of GCN5a relative to the essential KAT, GCN5b. While GCN5b localizes to coding regions, GCN5a surprisingly localizes exclusively to telomeres. These findings suggest that the loss of GCN5a leads to telomere dysfunction, which slows replication and promotes the transition to latency.

ORGANISM(S): Toxoplasma gondii

PROVIDER: GSE286090 | GEO | 2025/02/04

REPOSITORIES: GEO

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GCN5a is a telomeric lysine acetyltransferase whose loss primes Toxoplasma gondii for latency (CUT&Tag)

Project description:Toxoplasma gondii is a protozoan parasite that causes persistent infection in warm-blooded vertebrates by undergoing differentiation from a replicative stage (tachyzoites) to a latent encysted stage (bradyzoites). Stage differentiation is critical for transmission and pathogenesis and relies on gene regulation driven by a network of transcription and epigenetic factors. We previously found in non-cystogenic type I RH strain parasites that the lysine acetyltransferase (KAT), GCN5a, is dispensable in tachyzoites but required to upregulate stress-response genes, suggesting a link with bradyzoite conversion. To address this possibility, we generated endogenously tagged GCN5a parasites and a genetic knockout in cystogenic type II Pru strain. We show that GCN5a protein, but not mRNA, increases during differentiation and complexes with unique protein partners, most of which contain AP2 domains. Pru strain tachyzoites lacking GCN5a augment bradyzoite-specific gene expression in the absence of stress. Loss of GCN5a slowed tachyzoite replication and heightened sensitivity to bradyzoite conversion but resulted in smaller cyst sizes compared to wildtype. Using CUT&Tag, we delineated the chromosomal occupancy of GCN5a relative to the essential KAT, GCN5b. While GCN5b localizes to coding regions, GCN5a surprisingly localizes exclusively to telomeres. These findings suggest that the loss of GCN5a leads to telomere dysfunction, which slows replication and promotes the transition to latency.

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2022-08-12 | PXD033109 | Pride

Temporal analysis of in vivo Toxoplasma gondii cysts shows novel and late stage specific transcripts.

Project description:The protozoan pathogen Toxoplasma gondii has the unique ability to develop a chronic infection in the brain of its host. The T. gondii develops cysts within the neurons that are resilient against the host immune response and current therapeutics. The bradyzoite parasites within the cyst have a sugar-protein-rich wall and a slow-replication cycle, allowing them to remain hidden from the host. This intracellular encysted lifestyle of T. gondii has made them recalcitrant to molecular analysis in vivo. Here, we have enriched for T. gondii brain cysts 21 to 150 days post-infection (DPI). RNA and protein from bradyzoites was isolated from each timepoint. Deep sequencing of transcripts expressed during these three timepoints showed many of the identified proteins are transcriptionally expressed at a high level. Approximately one-third are more enriched during bradyzoite conditions compared to tachyzoites, and approximately half are expressed at similar levels during each phase. We have expanded the transcriptional profile of in vivo bradyzoites to 120 DPI. The RNA sequencing depth of in vivo bradyzoite T. gondii was over 250-fold greater than was have been previously, which allowed us to identify low level transcripts and novel bradyzoite-specific isoforms.

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