INDUCTION OF MCL1 EAT, BCL-2 RELATED GENE, BY RETINOIC ACID OR HEAT-SHOCK IN THE HUMAN EMBRYONAL CARCINOMA-CELLS, NCR-G3/

NCR-GS cells were established from a testicular embryonal carcinoma an d were differentiated into multi-lineages including trophectoderm cell s by exposure to retinoic acid. The differentiated cells began to prod uce human chorionic gonadotropin (hCG), a trophectoderm-specific hormo ne, which was regulated at the mRNA level. As we assumed that genes re sponsible for differentiation were differentially expressed at the ear ly stage of retinoic acid-induced differentiation, we prepared a cDNA library from retinoic acid-treated NCR-GS cells. This cDNA library was then screened for genes whose expression was induced during the diffe rentiation of these cells. From about 5 x 10(4) clones screened, three independent sequences were isolated. Sequencing analysis revealed tha t clone 1002 codes for mcl1/EAT, which has a Bcl-2 homology domain. Th e expression of mcl1/EAT, the Bcl-2 related gene, was increased at an early stage of the retinoic acid-induced differentiation and preceded the up-regulation of cytokeratin and hCG genes after ratinoic acid tre atment. Furthermore, mcl1/EAT was also up-regulated by heat shock, whi ch has recently been shown to induce the cells to differentiate.