Studies on the role of RecQ1 Helicase in the epigenetic memory of variant gene transcription in Plasmodium falciparum, the parasite that causes malaria

• Grant number: 24/00314-0
• Support Opportunities: Scholarships in Brazil - Master
• Start date: April 01, 2024
• End date: January 31, 2026
• Field of knowledge: Biological Sciences - Genetics
• Principal Investigator: Gerhard Wunderlich
• Grantee: Victória Simões Della Casa
• Host Institution: Instituto de Ciências Biomédicas (ICB). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

During the intraerythrocytic phase, the human malaria parasite Plasmodium falciparum exports several proteins to the surface of infected red blood cells. Among these proteins are members of the 45-90 alleles of the Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) family of proteins. These are important virulence factors because they cause cytoadherence and sequestration of infected red blood cells in deep vessels, a principal cause of severe malaria. Due to its exposure to the immune system, the expression of PfEMP1 antigens is strictly regulated by epigenetic events principally including chromatin modification. In consequence, only one active var gene encodes a PfEMP1 variant at a time on the surface of the infected red blood cell, while all other loci are silenced. After subsequent cycles of reinvasion into new red blood cells, the expression pattern of PfEMP1 (activation and silencing of var promoters) is normally maintained (epigenetic memory). It is not yet completely understood which components and in what sequence of events these drive the inheritance of var transcription patterns during subsequent cycles. Recently, the Helicase PfRecQ1 was identified as essential for the activation of active var loci and the knockout of PfRecQ1 led to the complete silencing of all var genes. However, it is unclear what recruits PfRecQ1 to loci var to be activated. We propose to evaluate what happens to the epigenetic memory once PfRecQ1 is reduced or removed from its place of action for just one or two cycles of reinvasion. This may inform the interaction/feedback of PfRecQ1 with factors that determine its recruitment to an initially active var locus. For this, two strains of modified parasites have already been prepared. In one lineage, the PfRecQ01 gene was tagged with sequences encoding the hemagglutinin (HA) tag followed by the self-cleaving peptide 2A, the neomycin/G418 resistance gene and a glmS ribozyme that allows subsequent selective degradation of the PfRecQ1-HA transcript. In the other strain, PfRecQ01 was tagged with 2xFKBP, GFP, 2A, neomycin resistance/G418, and a glmS domain. The second configuration allows conditional displacement of the tagged protein in the knock sideways system (after supertransfection of plasmid encoding the FRB ligand plus a secretion signal). We included as a positive control a strain where the heterochromatin protein 1 (HP1) was labeled in the same way. The study of factors that influence var transcription may reveal potential targets for intervention, as disruption of cytoadherence patterns in a natural infection situation (decreasing the specific pathogenic adhesive phenotype) can potentially alleviate symptoms of severe malaria and facilitate elimination of infected red blood cells.