m6A mRNA reader proteins in the AIDS-opportunistic pathogen Toxoplasma gondii

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Toxoplasma gondii is an intracellular parasite that causes life-threatening opportunistic infection in HIV/AIDS patients. The replicative stage (tachyzoite) develops into a latent stage (bradyzoite) that is impervious to immunity and approved antiparasitic drugs. Tissue cysts give rise to recurrent reactivation of infection in the immunocompromised, creating chronic disease in HIV/AIDS patients. Compounding this problem is a paucity of safe and effective therapies, which underscores the urgent need to identify essential processes in the parasite that could be exploited for the development of better drugs. We and others recently discovered that methylation of adenosines at position 6 (m6A) is abundant in Toxoplasma mRNA, representing a new layer of gene regulation called epitranscriptomics. Importantly, the proteins that “write” and “read” m6A modifications are essential for parasite viability. Moreover, as this machinery resembles plants more than humans, it represents an attractive new drug target. To study this vulnerability in Toxoplasma, we aim to fill the gap in our knowledge regarding how this signal dictates the fate of mRNA transcripts through the study of m6A reader proteins. We hypothesize that Toxoplasma m6A mRNA reader proteins coordinate different aspects of mRNA metabolism essential for parasite viability. In other species, m6A readers are found in the nucleus and cytosol, regulating the fate of mRNA by modulating splicing, trafficking, and translation. To date, only two nuclear YTH family m6A readers have been identified and they remain largely uncharacterized. And, despite the abundance of m6A mRNA in the cytosol, no cytosolic m6A readers have been identified. We propose two specific aims that will address our hypothesis by answering these questions. Aim 1 will determine the roles of the two plant-like YTH m6A readers operating in the Toxoplasma nucleus. Aim 2 will identify novel m6A reader proteins from tachyzoites and bradyzoites using a functional m6A-binding probe that we developed. These pioneering studies will mark the first detailed analysis of m6A readers in both replicative and latent stages of Toxoplasma, which promises to reveal new therapeutic options to treat this opportunistic infection of HIV/AIDS patients.