Browsing by Author "Srivastava, Sandeep"

Now showing 1 - 3 of 3
  • Thumbnail Image
    Item
    AP2XII-2 coordinates transcriptional repression for Toxoplasma gondii sexual commitment
    (bioRxiv, 2022) Srivastava, Sandeep; Holmes, Michael J.; White, Michael W.; Sullivan, William J., Jr.; Pharmacology and Toxicology, School of Medicine
    Toxoplasma gondii is a widespread protozoan parasite that has significant impact on human and veterinary health. The parasite undergoes a complex life cycle involving multiple hosts and developmental stages. How Toxoplasma transitions between life cycle stages is poorly understood, yet central to controlling transmission. Of particular neglect are the factors that contribute to its sexual development, which takes place exclusively in feline intestines. While epigenetic repressors have been shown to play an important role in silencing spurious gene expression of sexually committed parasites, the specific factors that recruit this generalized machinery to the appropriate genes remains largely unexplored. Here, we establish that a member of the AP2 transcription factor family, AP2XII-2, is targeted to genomic loci associated with sexually committed parasites along with the epigenetic regulators of transcriptional silencing, HDAC3 and MORC. Despite widespread association with gene promoters, AP2XII-2 is required for silencing of relatively few genes. Using CUT&Tag methodology, we identify two major genes associated with sexual development downstream of AP2XII-2 control, AP2X-10 and the amino acid hydroxylase AAH1. Our findings show that AP2XII-2 is a key contributor to the gene regulatory pathways modulating Toxoplasma sexual development. IMPORTANCE: Toxoplasma gondii is a parasite that undergoes its sexual stage exclusively in feline intestines, making cats a major source of transmission. A better understanding of the proteins controlling the parasite’s life cycle stage transitions is needed for the development of new therapies aimed to treat toxoplasmosis and transmission of the infection. Genes that regulate the sexual stages need to be turned on and off at the appropriate times, activities that are mediated by specific transcription factors that recruit general machinery to silence or activate gene expression. In this study, we identify a transcription factor called AP2XII-2 as being important for repression of a subset of sexual stage genes, including a sexual stage-specific AP2 factor (AP2X-10) and a protein (AAH1) required to construct the infectious oocysts expelled by infected cats.
  • Thumbnail Image
    Item
    Toxoplasma gondii AP2XII-2 Contributes to Proper Progression through S-Phase of the Cell Cycle
    (American Society for Microbiology, 2020-10-01) Srivastava, Sandeep; White, Michael W.; Sullivan, William J., Jr.; Pharmacology and Toxicology, School of Medicine
    Toxoplasma gondii is a protozoan parasite that causes lifelong chronic infection that can reactivate in immunocompromised individuals. Upon infection, the replicative stage (tachyzoite) converts into a latent tissue cyst stage (bradyzoite). Like other apicomplexans, T. gondii possesses an extensive lineage of proteins called ApiAP2s that contain DNA-binding domains first characterized in plants. The function of most ApiAP2s is unknown. We previously found that AP2IX-4 is a cell cycle-regulated ApiAP2 expressed only in dividing parasites as a putative transcriptional repressor. In this study, we purified proteins interacting with AP2IX-4, finding it to be a component of the recently characterized microrchidia (MORC) transcriptional repressor complex. We further analyzed AP2XII-2, another cell cycle-regulated factor that associates with AP2IX-4. We monitored parallel expression of AP2IX-4 and AP2XII-2 proteins in tachyzoites, detecting peak expression during S/M phase. Unlike AP2IX-4, which is dispensable in tachyzoites, loss of AP2XII-2 resulted in a slowed tachyzoite growth due to a delay in S-phase progression. We also found that AP2XII-2 depletion increased the frequency of bradyzoite differentiation in vitro. These results suggest that multiple AP2 factors collaborate to ensure proper cell cycle progression and tissue cyst formation in T. gondii. IMPORTANCE Toxoplasma gondii is a single-celled parasite that persists in its host by converting into a latent cyst stage. This work describes a new transcriptional factor called AP2XII-2 that plays a role in properly maintaining the growth rate of replicating parasites, which contributes to signals required for development into its dormant stage. Without AP2XII-2, Toxoplasma parasites experience a delay in their cell cycle that increases the frequency of latent cyst formation. In addition, we found that AP2XII-2 operates in a multisubunit complex with other AP2 factors and chromatin remodeling machinery that represses gene expression. These findings add to our understanding of how Toxoplasma parasites balance replication and dormancy, revealing novel points of potential therapeutic intervention to disrupt this clinically relevant process.
  • Thumbnail Image
    Item
    Toxoplasma gondii AP2XII-2 Contributes to Transcriptional Repression for Sexual Commitment
    (American Society for Microbiology, 2023) Srivastava, Sandeep; Holmes, Michael J.; White, Michael W.; Sullivan, William J., Jr.; Pharmacology and Toxicology, School of Medicine
    Toxoplasma gondii is a widespread protozoan parasite that has a significant impact on human and veterinary health. The parasite undergoes a complex life cycle involving multiple hosts and developmental stages. How Toxoplasma transitions between life cycle stages is poorly understood yet central to controlling transmission. Of particular neglect are the factors that contribute to its sexual development, which takes place exclusively in feline intestines. While epigenetic repressors have been shown to play an important role in silencing the spurious gene expression of sexually committed parasites, the specific factors that recruit this generalized machinery to the appropriate genes remain largely unexplored. Here, we establish that a member of the AP2 transcription factor family, AP2XII-2, is targeted to genomic loci associated with sexually committed parasites along with epigenetic regulators of transcriptional silencing, HDAC3 and MORC. Despite its widespread association with gene promoters, AP2XII-2 is required for the silencing of relatively few genes. Using the CUT&Tag (cleavage under targets and tagmentation) methodology, we identify two major genes associated with sexual development downstream of AP2XII-2 control, AP2X-10 and the amino acid hydroxylase AAH1. Our findings show that AP2XII-2 is a key contributor to the gene regulatory pathways modulating Toxoplasma sexual development. IMPORTANCE: Toxoplasma gondii is a parasite that undergoes its sexual stage exclusively in feline intestines, making cats a major source of transmission. A better understanding of the proteins controlling the parasite’s life cycle stage transitions is needed for the development of new therapies aimed at treating toxoplasmosis and the transmission of the infection. Genes that regulate the sexual stages need to be turned on and off at the appropriate times, activities that are mediated by specific transcription factors that recruit general machinery to silence or activate gene expression. In this study, we identify a transcription factor called AP2XII-2 as being important for the repression of a subset of sexual stage genes, including a sexual stage-specific AP2 factor (AP2X-10) and a protein (AAH1) required to construct the infectious oocysts expelled from infected cats.