Pinning NF-kappaB to the nucleus.

The peptidyl-prolyl isomerase Pin1 binds and stabilizes several phosphorylated transcription and mitosis regulators via its WW interacting domain. It is overexpressed in breast tumors and, as discuss in this issue of Molecular Cell, could account for their constitutive nuclear NF-kappaB expression. The proposed mechanism involves protection of Pin1-bound p65 against SOCS-1-mediated ubiquitination.