CHUK, A NEW MEMBER OF THE HELIX-LOOP-HELIX AND LEUCINE-ZIPPER FAMILIES OF INTERACTING PROTEINS, CONTAINS A SERINE THREONINE KINASE CATALYTIC DOMAIN

We have identified a new member of the helix-loop-helix (H-L-H) and le ucine zipper gene families via a reverse transcriptase-polymerase chai n reaction based strategy. This new gene, CHUK (conserved helix-loop-h elix ubiquitous kinase). may represent the founding member of a new cl ass of interacting chimeric proteins. The nucleotide sequence of a nea r full-length murine CHUK cDNA clone revealed an encoded polypeptide s pecifying: a carboxy-terminal H-L-H domain, an amino terminal serine-t hreonine kinase catalytic domain, and a leucine zipper-like amphipathi c cy-helix juxtaposed in between the H-L-H and kinase domains. CHUK is highly conserved in evolution and ubiquitously expressed in diverse t ypes of established cell lines, whereas it is differentially expressed in normal murine tissues. The structural features of the CHUK polypep tide suggest that its putative kinase activity may be targetted to H-L -H and/ or leucine zipper transcription factors. Alternatively, the du al amphipathic a helices may serve to control its intrinsic kinase act ivity by interactions with other cellular factors. CHUK may provide ne w insights into the regulated transmission of cytoplasmic signals to s pecific nuclear factors manifesting rapid alterations in patterns of c ellular gene expression.