Characterization of the mouse JAB1 cDNA and protein

JAB1 was originally described as a transcriptional coactivator of c-Jun and Jun D. Recent data suggests that JAB1 is a component of a large protein co mplex, the JAB1 signalosome in mammals and the COP9 complex in plants. The JAB1 signalosome is implicated in the phosphorylation of selected transcrip tion factors, while the COP9 complex is involved in repression of photomorp hogenesis in Arabidopsis. In this study, we describe the partial characteri zation of mouse JAB1 (mJAB1). The murine JAB1 protein is encoded by a gene located on mouse chromosome 1. mJAB1 mRNA is abundantly expressed in a vari ety of adult tissues as well as in mouse embryos. The JAB1 protein was read ily detectable in many cell types and localized to both the nucleus and cyt oplasm. Endogenous JAB1 protein is relatively stable and its degradation is not perturbed by blocking 26S proteasome activity, suggesting that this pr otein is not degraded by the ubiquitin-mediated proteolytic pathway. (C) 20 00 Elsevier Science B.V. All rights reserved.