MAP3K12 Binding Inhibitory Protein 1 (MBIP)

The C-terminal half has 2 leucine zipper-like motifs, which are predicted to form short amphipathic alpha helices, separated by a basic nuclear localization sequence. Northern blot analysis detected a 1.8-kb MBIP transcript in all tissues examined, with relatively high expression in heart and lung. MBIP localized in several nuclear patch-like structures following overexpression in COS-1 cells.When MBIP and MAP3K12 were coexpressed in COS-1 cells, the nuclear localization of MBIP was mostly abolished and cytoplasmic localization was apparent, likely due to MAP3K12 masking the MBIP nuclear localization signal. Binding also inhibited the ability of MAP3K12 to induce JNK activation. Among several JNK-activating pathways tested, the pathway induced by osmotic shock was the most sensitive to MBIP.