Figure 2. Phenotypic Switching of Sialic Acid Dependence Is Accompanied by a Reversible Increase in PfRh4 Promoter Accessibility.
(A) Schematic of a Southern blot using m6A-sensitive* restriction enzymes to measure chromatin accessibility at the PfRh4 promoter (K, KpnI; D, DpnI*; B, BglII; R, RsaI). The transcriptional start site and +1 nucleosome (black oval) are indicated. Gray boxes represent probe sequences.
(B) qRT-PCR analysis of PfRh4 expression in pEcDamLo schizonts, normalized to Dd2-pEcDamLo. Values represent mean and standard deviation of the quotient from an experiment performed in triplicate.
(C) Representative methylation-sensitive Southern blots assaying accessibility of DpnI sites. Position relative to ATG in parentheses. Percent methylation, shown below each graph, was calculated from band densities as (density + DpnI)/(density+DpnI + density−DpnI)*100. Arrowhead points to an additional band believed to represent a reported duplication of PfRh1 in the W2mef parasite lineage (Triglia et al., 2005).
(D) Levels of methylation in PfRh4-expressing and silenced parasites normalized to unselected Dd2-pEcDamLo. Values represent mean and range from two biological replicates for PfRh4 −215 and var2csa, mean and SD of four replicates for PfRh4 −1153 and a single experiment for PfRh1. See also Figure S2 and Table S2.
