Transcriptomic identification of IRP1- and IRP2-binding mRNAs. Fold enrichment of known IRE-containing mRNAs (Fth1, Tfrc, Slc11a2, Slc40a1, and Epas1) in IRP1 (A) or IRP2 (B) IPs versus mock controls was determined by qPCR. Gapdh and the non-IRE form of Slc11a2 were used as negative controls. Data show the values obtained with the first biologic replica used in microarray analysis; similar data were obtained with the second biologic replica (data not shown). (C) Heatmap visualization of microarray data (RMA analysis) for mRNAs copurified with IRP1 or IRP2. Fold-change values from 2 independent replicates for each tissue tested are given for probe sets that were detectable above background showing at least a 1.5-fold enrichment (log₂ ratio > 0.6). Red and black lines indicate positive and negative IP enrichment, respectively, relative to mock IPs. The color scales to the right indicate the magnitude of the fold change (base 2 logarithm) for a particular transcript. Number of mRNAs clustered by tissues is shown below each heatmap. (D) Number of mRNAs detected in each particular tissue bound by IRP1, IRP2, or IRP1 + IRP2.