(A) circRNA-RBP complex isolation from differentiated L-AN-5 cells followed by protein identification using mass spectrometry (LC-MS/MS). IP/Input ratios (based on IBAQ values) for selected RBPs (hnRNP L, hnRNP L, hnRNP U, DDX3X and DHX9) pulled down by circZNF827 are shown in left panel. In the right panel IP ratios of selected RBPs pulled down by circZNF827 relative to IP ratios for four other circRNAs (circTULP4, circHDGFRP3, circSLC8A1, and circZNF609) are shown. (B) RIP experiment evaluating interaction between circZNF827 and hnRNP K and -L in differentiated L-AN-5 cells. (C) RIP experiment evaluating interaction between both wildtype circZNF827 (WT) and circZNF827 with a deletion of predicted hnRNPK/L binding sites (hnRNPK/L mut) and hnRNP K and -L in the HEK293 Flp-In T-rex circZNF827 cell lines. Co-immunoprecipitation (co-IP) of both exogenously FLAG-tagged (D) and endogenously (E) expressed hnRNP K, -L and -U in HEK293 Flp-In T-rex cells with and without circZNF827 expression. GAPDH and HuR were used as loading controls in (D) and (E) respectively. (F) Western blot evaluating subcellular localization of hnRNP K in differentiated L-AN-5 cells upon circZNF827 knockdown. LARP1 and hnRNP C1/C2 were used for validation of the purity of the cytoplasmic and nuclear fractions. (G) Co-immunofluorescence (co-IF) of hnRNP K, -L and -U in HEK293 Flp-In T-rex cells upon circZNF827 overexpression. Arrows are pointing to hnRNP K- and hnRNP L-containing nuclear foci. Nuclei were visualized by DAPI staining. The scale bar indicates 10 μm. Irr: Irrelevant dishRNA. C: cytoplasmic fraction, N: nuclear fraction, T: total cell lysate. Data are depicted as mean ± SD (three biological replicates). (B), (E), and (H) One representative western blot is shown. Data shown in (A) and (C) are based on two and one replicates, respectively.