A novel protein MAJN binds to Jak3 and inhibits apoptosis induced by IL-2 deprival

To find a possible signal interacting with the Jak3 N-terminal, we screened the human peripheral blood cDNA library through both a two-hybrid system a nd a tyrosine-phosphorylation-modified two-hybrid system using: the N-termi nal of Jak3 as bait. Results showed that one new homologue of myosin heavy chain, designated MAJN (molecule associated with Jak3 N-terminal), could bi nd to Jak3 in a tyrosine-phosphorylation-independent manner. The interactio n between Jak3 and MAJN was further confirmed by immunoprecipitation in BAF -B03 beta cells. To investigate the function of MAJN, we have constructed t he BAF-B03 beta/MAJN cell line that stably expresses MAJN and found that ov erexpression of MAJN can partially inhibit the apoptosis induced by interle ukin-2 deprival. Further studies are needed to elucidate how MAJN executes its function to antagonize BAF-B03 beta cell death in the absence of IL-2. (C) 2000 Academic Press.