miR 17–92 cluster structure and expression. (A) Schematic representation of miR 17–92 cluster. Six miRNAs are expressed from intron 3 of C13orf25 gene (Ex = exon). The unfilled boxes correspond to precursor miRNAs and the solid thick black line within each box corresponds to mature miRNA. (B) The expression patterns of member miRNAs of miR 17–92 cluster in four PCa cell lines as evaluated by northern blotting (MDA = MDA PCa 2b). (C) Pairwise alignment of miRNAs. The figure reveals sequence similarities between miRNAs of paralogous clusters. Identical sequence between two miRNAs is shown by asterisks below the comparison and letters in bold correspond to sequence variation. miRs 18b and 20b shown in the alignments are derived from miR106a-363 cluster on chromosome X. The miR 106a-363 cluster contains six miRNAs, namely, 106a, 18b, 20b, 19b-2, 92a-2 and 363. The mature forms of miR 19b and miR 92a are expressed from both miR17–92 and miR106a-363 clusters.