APPEARANCE OF NUCLEAR PROTEASE ACTIVITY AFTER EMBRYONAL CARCINOMA-CELLS UNDERGO DIFFERENTIATION

Proteolytic systems are involved via multiple mechanisms in the regula tion of gene expression, including tightly controlled metabolism of tr anscription factors. In this study, we demonstrate that differentiatio n of mouse embryonal carcinoma cells to parietal endoderm-like cells i s accompanied by the appearance of nuclear protease activity. Interest ingly, this nuclear-associated protease activity is not observed in th e visceral endoderm-like cell line, PSA-5E, or in the differentiated c ells derived from both mouse embryonic stem cells and the human embryo nal carcinoma cell line NT2/D1. We also determined that this different iation-associated nuclear protease activity causes proteolysis of a wi de range of different transcription factors, including ATF-1, Sp1, NF- YA and B, and octamer-binding proteins Oct-1 and Oct-3. Based on the e ffects of specific inhibitors, the nuclear protease(s) can be classifi ed as a cysteine protease; however, lack of inhibition by calpastatin and EGTA distinguishes this protease activity from the calpain family of proteases. Given the properties of the differentiation-associated n uclear protease(s), we discuss the possibility that this protease(s) p lays a role in the metabolism of transcription factors during the diff erentiation of specific embryonic cells. (C) 1996 Academic Press, Inc.