Regulation of PIN1 expression in breast cancer. Upper part: Schematic representation of the human PIN1 gene, encompassing the promoter sequence, the 5' and 3' untranslated regions (UTRs), and exons 1–4 (Ex). Known cis-elements and the upstream signals and trans-acting factors are indicated; CSL Notch-responsive element. Middle part: Scheme of the mature PIN1 mRNA targeted by mir-200. Lower part: Schematic of the PIN1 protein structure with the sites of regulatory post-translational modifications and the responsible enzymes. The type IV WW domain, the linker region in between, and the PPIase domain are indicated. The nuclear localization signal is depicted as a small gray box within the PPIase domain. Modified aminoacid residues of PIN1 are indicated with a circle, enzymes acting on the specific residue with activating or repressing function on PIN1 are indicated in black boxed or in gray letters, respectively