CHARACTERIZATION OF FUNCTIONAL DOMAINS OF AN EMBRYONIC STEM-CELL COACTIVATOR UTF1 WHICH ARE CONSERVED AND ESSENTIAL FOR POTENTIATION OF ATF-2 ACTIVITY

We have recently cloned a cDNA encoding an embryonic stem cell transcr iptional coactivator termed UTF1 from the mouse F9 teratocarcinoma cel l line (Okuda, A, Fukushima, A., Nishimoto, M, Orimo, A., Yamagishi, T ., Nabeshima, Y., Kuro-o, M., Nabeshima, Y., Boon, a, Keaveney, M., St unnenberg, H.G., and Muramatsu, M. (1998) EMBO J. 17, 2019-2032). Here we have cloned a cDNA for human UTF1 and identified two highly conser ved domains termed conserved domain (CD)1 and CD2. Human UTF1, like th at of mouse, binds to ATF-2 and the mutagenesis analyses reveal that t he leucine zipper motif within the CD2 of the UTF1 and metal binding m otif of ATF-2 are involved in this interaction. The factor also binds to TATA-binding protein containing complex. By means of immunoprecipit ation analysis, we mapped two domains which are independently able to bind to the complex. Importantly, both domains are located within the conserved domains (one in CD1 and the other in CD2). Furthermore, tran sient transfection analyses point out the importance of these domains for activating ATF-2. Thus, these results suggest that these two conse rved domains identified here play important roles in activating specif ic transcription at least in part by supporting physical interaction b etween the upstream factor, ATF-2, and basal transcription machinery.