Mukae N, Enari M, Sakahira H, Fukuda Y, Inazawa J, Toh H, Nagata S
Department of Genetics, Osaka University Medical School, B-3, 2-2 Yamada-oka, Suita, Osaka 565-0871, Japan.
Proc Natl Acad Sci U S A. 1998 Aug 4;95(16):9123-8. doi: 10.1073/pnas.95.16.9123.
Caspase-activated DNase (CAD) cleaves chromosomal DNA during apoptosis. Here, we report isolation of two classes of human CAD cDNAs from a human KT-3 leukemic cell cDNA library. One class of cDNA encoded a protein comprising 338 amino acids, which showed a marked similarity to its murine counterpart. In vitro transcription and translation of this cDNA resulted in a functional CAD protein when the protein was synthesized in the presence of its inhibitor (inhibitor of CAD). The other cDNA class contained many deletions, insertions, and point mutations in the sequence corresponding to the coding region, suggesting that it is derived from a pseudogene. The functional CAD gene was localized to human chromosome 1p36.3 by fluorescent in situ hybridization. The CAD mRNA was expressed in a limited number of human tissues, including pancreas, spleen, prostate, and ovary. The expression of the CAD mRNA in human cell lines correlated with their ability to show DNA fragmentation during apoptosis. Overexpression of CAD potentiated DNA fragmentation by apoptotic stimuli in these cell lines, indicating that CAD is responsible for the apoptotic DNA degradation.
半胱天冬酶激活的脱氧核糖核酸酶（CAD）在细胞凋亡过程中切割染色体DNA。在此，我们报告从人KT-3白血病细胞cDNA文库中分离出两类人CAD cDNA。一类cDNA编码一种由338个氨基酸组成的蛋白质，该蛋白质与其鼠类对应物具有显著相似性。当在其抑制剂（CAD抑制剂）存在的情况下合成该蛋白质时，对该cDNA进行体外转录和翻译可产生功能性CAD蛋白。另一类cDNA在对应于编码区的序列中包含许多缺失、插入和点突变，表明它来源于一个假基因。通过荧光原位杂交将功能性CAD基因定位到人类染色体1p36.3。CAD mRNA在包括胰腺、脾脏、前列腺和卵巢在内的少数人类组织中表达。CAD mRNA在人类细胞系中的表达与其在细胞凋亡过程中显示DNA片段化的能力相关。在这些细胞系中，CAD的过表达增强了凋亡刺激引起的DNA片段化，表明CAD负责凋亡性DNA降解。
