miR106b-25 cluster structure and expression. (A) Genomic organization of miR106b-25 cluster in intron 13 of MCM7 gene. Precursor miRNAs are represented as unfilled boxes and the solid thick black line within each box corresponds to mature miRNA (Ex = exon). (B) Representative northern blot showing the expression of miR 106b-25 cluster in PCa cell lines (MDA = MDA PCa 2b). (C) Sequence comparison of miRNAs. Identical sequence between two miRNAs is shown by asterisks below the comparison and letters in bold correspond to sequence variation. miR 106a is expressed from miR106a-363 cluster on chromosome X. miR 92a is derived from both miR17–92 and miR106a-363 clusters. miR 20a is also expressed from the miR 17–92 cluster.