Fig. 3

SNHG4 sponges let-7a and regulates RRM2 expression. a miRNAs targeting RRM2 were predicted by ENCORI and TargetScan, and seven crossed miRNAs were identified and are shown in a Venn diagram. b LncRNAs targeting let-7 miRNAs were predicted by ENCORI, and five lncRNAs were predicted to be their common upstream lncRNAs. c Spearman’s correlation coefficient test showed the correlation between the expression of RRM2 and SNHG4 in 499 PCa tissue samples from the TCGA_PRAD dataset (R = 0.45, p < 0.001). d and e SNHG4 was overexpressed or knocked down in PCa cells, and RRM2 expression was measured by qRT‒PCR and western blotting. f The sequences of predicted binding sites between SNHG4, let-7 miRNAs and RRM2 are shown. g and h Let-7a-5p was overexpressed or knocked down in PCa cells, and RRM2 expression was analyzed by qRT‒PCR and western blotting. i and j A dual-luciferase reporter assay was performed to assess the binding between let-7a and the 3’UTR of the RRM2 gene in 22Rv1 and LNCaP cells. k RIP assay indicating the enrichment of SNHG4, let-7a and RRM2 in the RNA products pulled down by anti-IgG/anti-AGO antibody before or after SNHG4 overexpression. l and m A dual-luciferase reporter assay was performed to assess the binding between SNHG4 and let-7a in 22Rv1 and LNCaP cells. Full-length SNHG4 or binding site-mutated SNHG4 was cloned into luciferase plasmids. n and o Expression of RRM2 was measured in control cells, SNHG4-overexpressing cells or SNHG4 and let-7a double-overexpressing cells by qRT‒PCR and western blot. ns indicates not significant, * indicates p < 0.05, ** indicates p < 0.01