Fig. 3. Model of JAB1/CSN5 function in regulating AP-1 mediated transcription. Line colors relate to specific functions: blue, c-Jun mediated transactivation; pink, hormone receptor mediated transactivation. Thin lines ending with filled circles represent inhibitory interactions. Thin lines ending with closed arrow heads represent stimulatory interactions. Dotted lines show protein movement. JAB1/CSN5 mediates AP-1 transactivation through c-Jun. Interaction of JAB1 with LFA-1, MIF or LHR inhibits AP-1 transactivation. Extracellular substrate binding to LFA-1 releases JAB1 which redistributes to the nucleus leading to AP-1 transactivation. Binding of JAB1/CSN5 to PR and SRC-1 also induces AP-1 transactivation. The protein–protein interactions within the CSN are not specified (reviewed in Kapelari et al., 2000). CSN, COP9 signalosome.