Fig. 3
Cancer hotspots in DICER1 RNase IIIb and RNase IIIa domains deplete 5p miRNAs. a Existing model for how the two RNase III domains of Dicer cleave a pre-miRNA hairpin, and for strand-specific defects in RNase IIIb cancer hotspot mutants. b Volcano plots of miRNA-5p (green) and miRNA-3p (blue) expression in sets of Uterine Corpus Endometrial Cancer (UCEC) cases. Top: control comparison of randomly selected DICER1-wt (15 vs. bulk 533 cases) shows only incidental fluctuation of miRNA levels. Bottom: comparison of 15 RNase IIIb hotspot mutant to 548 DICER1-wt UCEC cases shows downregulation of miRNA-5p species and upregulation of miRNA-3p species. c Barplots of the same UCEC comparisons showing that RNase IIIb hotspot cases with overt biallelic-inactivating mutations (four datasets) distort miRNA-5p/3p profiles more severely than other RNase IIIb hotspot cases (11 datasets). d Systematic analysis of relative miRNA strand processing in TCGA small RNA-seq data. We calculated a metric (mi53) that summarizes sample-specific relative 5p abundances. The few samples with negative values are dominated by RNase IIIb hotspot mutants. e Segregation of TCGA samples by genotype. For this analysis, the ovarian serous cystadenocarcinoma cancer (OV) cohort was omitted, due to tissue-specific low mi53 score (Supplementary Fig. 6). DICER1 mutant samples stratify according to whether they have RNase IIIb hotspot mutants with biallelic-inactivating mutations (in red), or have RNase IIIb hotspots accompanied by other alterations of unknown consequence or lack secondary mutations (in orange). The remainder of DICER1 mutant samples behave similarly to DICER1-wt samples, with the exception of S1344L cases (in green), which also exhibit miRNA-5p depletion. f The mi53 metric varies according to the miRNAs expressed in a given tissue. Segregating DICER1-RNase III hotspot cases by tumor type illustrates that biallelic hotspot cases (which include all S1344L cases) typically exhibit lowest mi53 scores within their cohort, whereas other RNase III hotspot cases are more heterogeneous in their behavior. Box plot elements: center line, median; box limits, upper and lower quartiles; whiskers, 1.5x interquartile range
