HMGB1 is required for virulence gene expression via configuration of genome architecture in Plasmodium falciparum [RNA-seq]

The mutually exclusive expression of virulence genes is critical for the immune evasion and pathogenesis of malaria parasites, Plasmodium falciparum, in human host. The three-dimensional genome structure has emerged as a new factor involved in transcriptional regulation of virulence gene families in the parasites. However, the mechanism controlling this epigenetic regulation pathway remains elusive. Here, we have identified the highly conserved high mobility group protein HMGB1 as a critical architectural regulator in establishment of high-order genome structure via interaction with centromeres in P. falciparum. Genetic manipulation of Pfhmgb1 gene and Hi-C analysis showed that the boundary of telomere and centromere clusters in an opposite spatial relationship in the nucleus was disrupted upon hmgb1 knockout. The collapse of euchromatic centromere cluster from nuclear periphery towards the opposite heterochromatic telomere cluster triggered relocation of the original active var gene, which resulted in complete silence of the entire repertoire of var gene family. ChIP-seq and fluorescence assay analysis confirmed the specific interaction between PfHMGB1 and centromeres. Meanwhile, as in other eukaryotes, PfHMGB1 was also widely present on the promoter regions of a variety of genes and co-regulated transcription, including other non-var variant gene families, suggesting multiple dimensions of epigenetic gene regulation by PfHMGB1. Finally, the natural genome organization could be reconstructed by hmgb1 gene complementation, which rescued the mutually exclusive expression of virulence genes. Taken together, our work provides new insight into the evolution of biological functions of the HMG architectural superfamily in eukaryotes. Expression profiling by high throughput sequencing(RNA-seq) in the P. falciparum for wt ,PfHMGB1-ko and Pfhmgb1-rescue parasites