miR23b-24 cluster structure and expression. (A) Three miRNAs are encoded in intron 15 of AMPO gene (Ex = exon). Precursor miRNAs are represented as unfilled boxes and the solid thick black line within each box corresponds to mature miRNA. (B) Representative northern blot showing the expression of miR 23b-24 in PCa cell lines (MDA = MDA PCa 2b). (C) Aligned sequences of mature miRNAs revealing the high level of identity. Asterisks correspond to identical sequence between two miRNAs and bold letters corresponds to sequence variation. miRs 23a and 27a are expressed from the miR 23a-24 cluster on chromosome 19.