Yersinia inhibits host signaling by acetylating MAPK kinases

Pathogenic Yersinia spp. secrete the effector YopJ ( YopP) into host cells to counteract cytokine production and to induce programmed cell death ( apoptosis). YopJ achieves these aims by inactivating mitogen-activated protein kinase ( MAPK) and nuclear factor kappa B signaling pathways. YopJ was shown to bind to members of the MAPK kinase ( MKK) family and was predicted to have protease activity toward ubiquitin ( Ub)like proteins. In a recent report, YopJ was demonstrated to inactivate MKKs via acetylation of critical serine or threonine residues. The rami. cations of these exciting results are discussed in the context of other studies implicating YopJ as a Ub- like protease.