Investigation of NOT1 proteins in regulating gene expression in plasmodium falciparum

Abstract

Plasmodium falciparum is the most deadly form of malaria that threatens millions of people around the world. The CCR4-NOT complex is a highly conserved complex that regulates gene expression across the eukaryotic kingdom and NOT1 is the scaffold of the complex. P. falciparum encodes two paralogs of NOT1, NOT1.1 (PF3D7_1103800) and NOT1.2 (PF3D7_1417200). My study investigates the function of two NOT1 proteins in gene regulation during the 48-hour intraerythrocytic developmental cycle. I found that NOT1.1 and NOT1.2 are probably the scaffold of the complex in P. falciparum, interacting with CAF1, CCR4, CAF40 as well as NOT4 subunits. The independent mutation of Not1.1 and Not1.2 leads to altered mRNA abundance of many genes, including many egress- and invasion-related genes, which may result in defective growth and invasion rate. The knockout of Not1.1 affects recruitment of the elongating form of RNA Polymerase II, which however is not significantly correlated to differential mRNA abundance, suggesting the role of NOT1.1 in post-transcriptional regulation. In addition, comparison between the differential mRNA abundance in the two mutants reveals a negative correlation, demonstrating opposite functions of NOT1.1 and NOT1.2 in gene regulation. Furthermore, I found that differential mRNA abundance in the two mutants is correlated to that in Caf1 mutant and Alba1 mutant. I propose that NOT1.1 and NOT1.2 compete to be the scaffold of the CCR4-NOT complex and regulate gene expression post-transcriptionally by modulating the functions of their interacting proteins, including CAF1 and ALBA1, which are key players in mRNA metabolism.