A role for the poly-asparagine repeat in the Plasmodium histone acetyltransferase, PfGCN5

Plasmodium falciparum possesses one of the most AT-rich genomes in nature (80.6%). A consequence is an asparagine-rich proteome. A quarter of P. falciparum proteins possess poly-asparagine repeats that can extend more than 100 residues. The role of these repeats has remained a mystery in the biology of this parasite. Here, we find that the poly-asparagine repeat-containing N terminus of the histone acetyltransferase PfGCN5 associates with the C-terminal catalytic domain after cleavage in the nucleus. Deletion of the repeat destabilizes the N-terminal polypeptide, leading to impaired parasite development and growth, particularly under stress conditions. Using high-resolution mass spectrometry and western blotting analysis, we uncovered a profound effect of the poly-asparagine repeat on acetylation of histones H3, H3.3, and H4. These findings suggest that the poly-asparagine repeat contributes to PfGCN5 acetyltransferase activity, a role previously attributed solely to its C-terminal domain. This report of a function for a poly-asparagine repeat in P. falciparum expands our understanding of a pervasive characteristic of its proteome.