MAIL, a novel nuclear I kappa B protein that potentiates LPS-induced IL-6 production.

We have identified and characterized a novel member of the ankyrin-repeat family named 'molecule possessing ankyrin-repeats induced by lipopolysaccharide' (MAIL). The C-terminal portion of MAIL shared high sequence homology with the I kappa B family. Intraperitoneal injection of lipopolysaccharide (LPS) into mice rapidly (<0.5 h) induced MAIL mRNA in various tissues, particularly in the spleen, lymph node, and lung. Ectopically expressed MAIL was localized in the nucleus, and remarkably potentiated the LPS-induced mRNA expression and secretion of interleukin (IL)-6 in Swiss 3T3 cells. These findings indicate that MAIL is one of the nuclear I kappa B proteins and an activator of IL-6 production.