PfTPx-1 is localized to the active var expression site in ring-stage parasites. (A) Immunofluorescence microscopy of PfTPx-1, endogenously tagged with HAx3 in ring (Upper) and schizont (Lower) parasites. Nuclei are stained with DAPI. (Scale bar, 2 μm.) (B) Superresolution STORM imaging of tightly synchronized ring-stage parasites (∼18 h postinfection) expressing PfTPx-1HAx3. Nuclei stained with YOYO1 were imaged by conventional epif luorescence for cellular orientation. (Scale bar, 0.5 μm.) (C) Cellular fractionation of synchronized ring and late-stage parasites was performed on the PfTPx-1HAglmS line and nuclear and cytoplasmic extracts (NE and CE, respectively). PfTPx-1 was detected with anti-HA, antialdolase was used as a cytoplasmic marker, and antihistone H3 as a nuclear marker. (D) RNAFISH, of var2csa-expressing parasites that episomally express sfGFP-PfTPx-1 fusion (green), using custom-designed Stellaris probes that hybridize to var2csa (red). In all nuclei (n = 111) PfTPx-1 was found to overlap with the active var mRNA. (Scale bar, 1 μm.). Heinberg A, Amit-Avraham I, Mitesser V, Simantov K, Goyal M, Nevo Y, Kandelis-Shalev S, Thompson E, Dzikowski R. A nuclear redox sensor modulates gene activation and var switching in Plasmodium falciparum. Proc Natl Acad Sci U S A. 2022 119(33):e2201247119. PMID: 35939693