PfAP2-HC, an unusual, heterochromatin-associated ApiAP2 factor of Plasmodium falciparum

In this study we have investigated PfAP2-HC (PF3D7_1456000), a protein that was identified by co-immunoprecipitation with PfHP1 coupled with liquid chromatography-tandem mass spectrometry. PfAP2-HC belongs to the ApiAP2 family, the main transcription factor family in Apicomplexan parasites. We have confirmed that AP2-HC colocalises with HP1 with the use of immunofluorescence assays and chromatin immunoprecipitation-sequencing. We show that PfAP2-HC is not required for heterochromatin maintenance and inheritance with the use of PfAP2-HC Kock out and knockdown. We show with transcriptome-wide microarray time course analysis that PfAP2-HC does not act as a transcription factor in blood stage parasites. We demonstrate that the AP2 domain is dispensable for heterochromatin targeting by introducing a premature stop codon before the AP2 domain. We show that PfAP2-HC binding to heterochromatin dependents on PfHP1. and PfAP2-HC is likely not involved in de novo heterochromatin formation Overall design: 17 samples were analysed, 11 ChIP samples (7 PfHP1 and 4 GFP) and 6 input control samples. Biological replicates for the HP1mSglmSON samples were performed, to eliminate experimental error, due to the abstains of signal in the GFP ChIP (AP2-HC/AP2-14)