Monoallelic expression of var gene family is controlled by chromatin-associated RNase II (PFI0295c). a, Two-colour RNA-FISH of var transcripts in PfRNase II–FKBP-H3 and G1 clones. Red, UpsC-type C1 var probe (PFD0625c); green, upsA-type A1 var (PFF0020c). Co., co-localization; adj., adjacent; non-co., non-co-localization. Nuclear DNA was stained by DAPI (blue). Scale bar, 1 mm. b, Live-cell IFA using antisera to various PfEMP1s to detect co-expression of var genes in PfRNase II–FKBP H3 and G1 clones, respectively. The 3D7-G7 control expresses only one type of PfEMP1 (C1 var). Scale bar, 5 mm. c, PfRNase II is linked to the silent var-associated loci. Left: combined FISH/IFA assay using anti-PfRNase II antibody (IFA) with a FISHprobe (PFF0020c) that detected the upsA var expression site (RNA-FISH) in PfRNase II–FKBP clone H3. The same upsA var gene (DNA-FISH/IFA) was also analysed in ring-stage 3D7-G7 parasites.Zhang Q, Siegel TN, Martins RM, Wang F, Cao J, Gao Q, Cheng X, Jiang L, Hon CC, Scheidig-Benatar C, Sakamoto H, Turner L, Jensen AT, Claes A, Guizetti J, Malmquist NA, Scherf A. Exonuclease-mediated degradation of nascent RNA silences genes linked to severe malaria. Nature. 2014 Jun 29.