Halenbeck R, MacDonald H, Roulston A, Chen T T, Conroy L, Williams L T
Chiron Corporation, 4560 Horton Street, Emeryville, California 94608, USA.
Curr Biol. 1998 Apr 23;8(9):537-40. doi: 10.1016/s0960-9822(98)79298-x.
Induction of apoptosis by death receptors such as Fas or tumour necrosis factor (TNF) R1 leads to distinct changes in cell morphology, activation of the caspase protease cascade, and the degradation of nuclear chromatin by activated nucleases. Here, we describe the purification and cDNA cloning of a novel 40 kDa endonuclease from Jurkat cells that is activated by caspases. This protein, designated caspase-activated nuclease (CPAN), is sufficient to degrade naked DNA and to induce apoptotic morphology and DNA fragmentation in naive nuclei. CPAN is highly homologous to a recently described mouse nuclease, CAD [1], and may represent the human homologue. Our data on the human cDNA as well as additional data on the mouse homologue suggest that a 30 amino-acid portion of the recently published mouse sequence [1] is incorrect. We show that the activity of human CPAN is regulated by DFF45 [2], an inhibitor necessary for CPAN expression and stabilization in an inactive state in living cells. Proteolytic cleavage of DFF45 by caspases in vitro leads to dissociation of DFF45 fragments from CPAN and activation of CPAN as an endonuclease. CPAN is a tightly regulated endonuclease with unique characteristics that might represent a distinctive family of endonucleases.
Fas或肿瘤坏死因子（TNF）R1等死亡受体诱导细胞凋亡会导致细胞形态发生明显变化、半胱天冬酶蛋白酶级联反应激活以及活化的核酸酶对核染色质的降解。在此，我们描述了一种来自Jurkat细胞的新型40 kDa核酸酶的纯化及cDNA克隆，该核酸酶可被半胱天冬酶激活。这种蛋白被命名为半胱天冬酶激活核酸酶（CPAN），它足以降解裸露的DNA，并在天然细胞核中诱导凋亡形态和DNA片段化。CPAN与最近描述的一种小鼠核酸酶CAD高度同源，可能代表人类同源物。我们关于人类cDNA的数据以及关于小鼠同源物的其他数据表明，最近发表的小鼠序列中的一个30个氨基酸的部分是错误的。我们发现人类CPAN的活性受DFF45调节，DFF45是一种在活细胞中CPAN以无活性状态表达和稳定所必需的抑制剂。半胱天冬酶在体外对DFF45的蛋白水解切割导致DFF45片段与CPAN解离，并激活CPAN作为核酸酶的活性。CPAN是一种受到严格调控的核酸酶，具有独特的特性，可能代表一个独特的核酸酶家族。
