CHUK (conserved helix-loop-helix ubiquitous kinase) is ubiquitously expressed in diverse types of established cell lines, whereas it is differentially expressed in normal murine tissues. The structural features of the CHUK polypeptide suggest that its putative kinase activity may be targetted to H-L-H and/or leucine zipper transcription factors. Alternatively, the dual amphipathic a-helices may serve to control its intrinsic kinase activity by interactions with other cellular factors. CHUK may provide new insights into the regulated transmission of cytoplasmic signals to specific nuclear factors manifesting rapid alterations in patterns of cellular gene expression. The non-canonical NF-κB activating kinase IKKα, encoded by CHUK, modulates pro- or anti-inflammatory responses, cellular survival, and cellular differentiation. CHUK has an essential role in the development of the skin epidermis and its derivatives, along with various other morphogenetic events.