Molecular basis for the direct inhibition of AP-1 DNA binding by 15-deoxy-Δ12,14-prostaglandin J2

Cyclopentenone prostaglandins may interfere with cellular functions by multiple mechanisms. The cyclopentenone 15-deoxy-Delta(12,14)-prostaglandin J(2) (15d- PGJ(2)) has been reported to inhibit the activity of the transcription factor AP-1 in several experimental settings. We have explored the possibility of a direct interaction of 15d- PGJ(2) with AP-1 proteins. Here we show that 15d-PGJ(2) covalently modifies c-Jun and directly inhibits the DNA binding activity of AP-1. The modification of c-Jun occurs both in vitro and in intact cells as detected by labeling with biotinylated 15d- PGJ(2) and mass spectrometry analysis. Attachment of the cyclopentenone prostaglandin occurs at cysteine 269, which is located in the c-Jun DNA binding domain. In addition, 15d- PGJ(2) can promote the oligomerization of a fraction of c-Jun through the formation of intermolecular disulfide bonds or 15d-PGJ(2)-bonded dimers. Our results identify a novel site of interaction of 15d- PGJ(2) with the AP-1 activation pathway that may contribute to the complex effects of cyclopentenone prostaglandins on the cellular response to pro-inflammatory agents. They also show the first evidence for the induction of protein cross-linking by 15d- PGJ(2).