Scholtz B, Lamb K, Rosfjord E, Kingsley M, Rizzino A
Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha 68198-6805, USA.
Dev Biol. 1996 Feb 1;173(2):420-7. doi: 10.1006/dbio.1996.0037.
Proteolytic systems are involved via multiple mechanisms in the regulation of gene expression, including tightly controlled metabolism of transcription factors. In this study, we demonstrate that differentiation of mouse embryonal carcinoma cells to parietal endoderm-like cells is accompanied by the appearance of nuclear protease activity. Interestingly, this nuclear-associated protease activity is not observed in the visceral endoderm-like cell line, PSA-5E, or in the differentiated cells derived from both mouse embryonic stem cells and the human embryonal carcinoma cell line NT2/D1. We also determined that this differentiation-associated nuclear protease activity causes proteolysis of a wide 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 effects of specific inhibitors, the nuclear protease(s) can be classified 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 nuclear protease(s), we discuss the possibility that this protease(s) plays a role in the metabolism of transcription factors during the differentiation of specific embryonic cells.
蛋白水解系统通过多种机制参与基因表达的调控，包括对转录因子进行严格控制的代谢过程。在本研究中，我们证明小鼠胚胎癌细胞向壁内胚层样细胞的分化伴随着核蛋白酶活性的出现。有趣的是，在内脏内胚层样细胞系PSA-5E中，或在源自小鼠胚胎干细胞和人胚胎癌细胞系NT2/D1的分化细胞中，均未观察到这种与核相关的蛋白酶活性。我们还确定，这种与分化相关的核蛋白酶活性会导致多种不同转录因子的蛋白水解，包括ATF-1、Sp1、NF-YA和B，以及八聚体结合蛋白Oct-1和Oct-3。基于特定抑制剂的作用，该核蛋白酶可归类为半胱氨酸蛋白酶；然而，钙蛋白酶抑制蛋白和乙二醇双乙胺醚四乙酸（EGTA）对其无抑制作用，这使得这种蛋白酶活性与钙蛋白酶家族的蛋白酶有所不同。鉴于与分化相关的核蛋白酶的特性，我们讨论了这种蛋白酶在特定胚胎细胞分化过程中参与转录因子代谢的可能性。
