Phase separation of Heterochromatin protein 1 (HP1) controls virulence gene silencing in Plasmodium falciparum [RNA-seq]

ABSTRACT: Malaria caused by Plasmodium falciparum involves antigenic variation on the infected red blood cells through mutually exclusive expression of var genes. The repressed var genes have a distinct genome organization where they localize as a cluster near the nuclear periphery and are bound by PfHP1 (P. falciparum Heterochromatin Protein 1). However, the mode of regulation of var genes by PfHP1 remains unclear. In this study, we show that PfHP1 undergoes liquid-liquid phase separation (LLPS) in vitro in an RNA and DNA-dependent manner. Single-molecule DNA tethering experiments further revealed that AT-rich DNA sequences act as nucleation sites for the assembly and compaction of PfHP1-mediated heterochromatinization. We have also identified point mutations in the IDRs (intrinsically disordered regions) of PfHP1 that disrupt its phase separation as well as DNA compaction in vitro. An ectopic expression of PfHP1 phase separation and DNA compaction mutants led to dispersed nuclear localization, in contrast to the punctate appearance of the wild-type protein and altered chromatin binding at var genes. These results were corroborated with DiCre/loxP based conditional expression of the same PfHP1 mutants, which also led to the de-repression of multiple var genes (as many as 54 out of 60 var genes), mimicking the phenotype of PfHP1 depletion mutants. To assess the dynamic properties of PfHP1 condensates in vivo, we performed fluorescence recovery after photobleaching (FRAP) in live parasites, which revealed rapid fluorescence recovery, supporting their liquid-like behaviour. In conclusion, our study demonstrates the role of PfHP1 mediated LLPS in formation of heterochromatin and var gene silencing; unveiling a fundamental mechanism that drives antigenic variation in P. Falciparum.

ORGANISM(S): Plasmodium falciparum

PROVIDER: GSE300206 | GEO | 2026/02/16

REPOSITORIES: GEO