Investigating the druggability and biological roles of Apicomplexan AP2 transcription factors in the human malaria parasite Plasmodium falciparum
Open Access
- Author:
- Russell, Timothy
- Graduate Program:
- Biochemistry, Microbiology, and Molecular Biology
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- September 28, 2022
- Committee Members:
- David Gilmour, Major Field Member
Scott Showalter, Outside Unit & Field Member
Scott Lindner, Major Field Member
Manuel Llinas, Chair & Dissertation Advisor
Wendy Hanna-Rose, Program Head/Chair
C Okafor, Major Field Member
Frank Pugh, Special Member - Keywords:
- Plasmodium falciparum
ApiAP2 proteins
Gene Regulation
Antimalarial drugs - Abstract:
- Plasmodium falciparum, the most virulent of the human infectious malaria parasites, caused over 600,000 deaths in 2020. Alarmingly, malaria deaths have increased since 2019 and resistance has been reported for every antimalarial drug deployed to date. Regulation of gene expression is critical for P. falciparum to complete its complex life cycle, which includes stages in the human host and Anopheles mosquito vector. Gene regulation in malaria parasites is primarily driven by the Apicomplexan AP2 (ApiAP2) proteins, a single expanded family of sequence specific DNA binding transcription factors. ApiAP2 proteins are plant derived and therefore have no homologs encoded in the human or mosquito genomes, making them potential drug targets. In order to exploit ApiAP2 proteins as antimalarial intervention targets, it is important to both identify ApiAP2 inhibitors and to probe the biological function of ApiAP2 proteins. In this thesis work, ApiAP2 proteins have been investigated to assess their biological functions and druggability. In Chapter 2, putative competitors of DNA binding by the ApiAP2 protein AP2-EXP were selected using an in silico screen. Several compounds were found to inhibit ApiAP2 DNA binding in vitro using DNA gel-shifts. An ApiAP2 competitor compound was then leveraged for use as a chemical genetic tool to interrogate the function of AP2-EXP. In Chapter 3, a potential cooperative interaction between the ApiAP2 proteins PfAP2-I and PfAP2-G during P. falciparum sexual development was interrogated by mapping the DNA binding occupancy of each protein. PfAP2-I genomic occupancy changes in the presence of PfAP2-G, indicating for the first time a causal relationship between two P. falciparum transcription factors that regulates DNA binding specificity. PfAP2-I and PfAP2-G co-occupancy coincides with the activation of P. falciparum sexual stage genes. In Chapter 4, the first indications of the gene regulatory functions of the ApiAP2 proteins PfAP2-HS and PfAP2-O3 were uncovered by mapping their genome-wide DNA binding occupancies. PfAP2-HS was found to regulate a transcription program that is required for P. falciparum to survive febrile host temperatures, while PfAP2-O3 primarily occupies the gene bodies of loci encoding tRNA and rRNA during sexual development. In aggregate, this thesis work describes efforts to further understand the unique ApiAP2 transcription factor proteins in the human malaria parasite P. falciparum.