Fig. 1

Heme binding reverses the orientation of Microprocessor on pri-miRs. a Domain organization and construct diagrams for Drosha and DGCR8. Recombinant protein complexes were purified after coexpressing the highlighted regions (magenta). Coexpression of Drosha with DGCR8^Heme, DGCR8^Apo, and DGCR8^C352S yields MP^Heme, MP^Apo, and MP^C352S, respectively. CED central domain, RIIID ribonuclease III domain, dsRBD double-stranded RNA-binding domain, HBR heme-binding region, CTT C-terminal tail. b In vitro pri-miR processing assay using 5′ end-radiolabeled pri-miR-143. Reactions involving MP^Heme (130 nM), MP^Apo (130 nM) and MP^C352S (260 nM) are shown. Correct product is shown with a black asterisk, incorrect product is shown with a red asterisk. c In vitro pri-miR processing assays used to orient the RIIID domains of Drosha on a pri-miR, with diagram shown to the right. Substrate shown is pri-miR-21. d Model depicting the heme-induced reversal of Drosha/DGCR8 complex