Fig. 5.

GRSF1 binds and melts G4 RNAs in vitro, which is dependent on qRRM domains. a Analysis of the ability of wild type or mutated GRSF1 to melt G4 structures. Mutated GRSF1 harbors point mutations in qRRM domains. Fluorophore and quencher assays were performed. b Confirmation that wild-type GRSF1 targets G4 structures. Different ionic conditions that are known to affect G4 structure stability were applied. The presence of potassium ions stabilizes G4 whereas the structures are less stable in the presence of lithium ions. c, d ThT in vitro assay of mitochondrial G4 RNAs, which are upregulated in GRSF1- or degradosome-deficient cells. Wild type (c) or mutated (d) GRSF1 was examined. Bars represent average values from three independent replicates. Error bars and blue dots represent standard deviation and individual values, respectively (a–d). e CD (220–300 nm) spectra of Mito3 RNA, GRSF1, or mixture of thereof. f EMSA assays of indicated substrates. The tRNA-like mutant has mutated G-tracts. See also Supplementary Fig. 5b, c and Supplementary Fig. 7