CIKS, a connection to IκB kinase and stress-activated protein kinase

Pathogens, inflammatory signals, and stress cause acute transcriptional responses in cells. The induced expression of genes in response to these signals invariably involves transcription factors of the NF-kappa B and AP-1/ATF families, Activation of NF-kappa B factors is thought to be mediated primarily via I kappa B kinases (IKK), whereas that of AP-1/ATF can be mediated by stress-activated protein kinases (SAPKs; also named Jun kinases or JNKs). IKK alpha and IKK beta are two catalytic subunits of a core IKK complex that also contains the regulatory subunit NEMO (NF-kappa B essential modulator)/IKK gamma. The latter protein is essential for activation of the IKKs. but its mechanism of action is not known. Here we describe the molecular cloning of CIKS (connection to IKK and SAPK/JNK), a previously unknown protein that directly interacts with NEMO/IKK gamma in cells. When ectopically expressed, CIKS stimulates IKK and SAPK/JNK kinases and it transactivates an NF-kappa B-dependent reporter. Activation of NF-kappa B is prevented in the presence of kinase-deficient. interfering mutants of the IKKs. CIKS may help to connect upstream signaling events to IKK and SAPK/JNK modules. CIKS could coordinate the activation of two stress-induced signaling pathways. functions reminiscent of those noted for tumor necrosis factor receptor-associated factor adaptor proteins.