Shiokawa D, Tanuma S
Department of Biochemistry, Faculty of Pharmaceutical Sciences, Science University of Tokyo, 12 Funagawara-machi, Ichigaya, Shinjuku-ku, Tokyo 162-0826, Japan.
Biochemistry. 2001 Jan 9;40(1):143-52. doi: 10.1021/bi001041a.
We describe here the characterization of the so far identified human DNase I family DNases, DNase I, DNase X, DNase gamma, and DNAS1L2. The DNase I family genes are found to be expressed with different tissue specificities and suggested to play unique physiological roles. All the recombinant DNases are shown to be Ca(2+)/Mg(2+)-dependent endonucleases and catalyze DNA hydrolysis to produce 3'-OH/5'-P ends. High activities for DNase I, DNase X, and DNase gamma are observed under neutral conditions, whereas DNAS1L2 shows its maximum activity at acidic pH. These enzymes have also some other peculiarities: different sensitivities to G-actin, aurintricarboxylic acid, and metal ions are observed. Using a transient expression system in HeLa S3 cells, the possible involvement of the DNases in apoptosis was examined. The ectopic expression of each DNase has no toxic effect on the host cells; however, extensive DNA fragmentation is observed only in DNase gamma-transfected cells after the induction of apoptosis. Furthermore, DNase gamma is revealed to be located at the perinuclear region in living cells, and to translocate into the nucleus during apoptosis. Our results demonstrate that DNase I, DNase X, DNase gamma, and DNAS1L2 have similar but unique endonuclease activities, and that among DNase I family DNases, DNase gamma is capable of producing apoptotic DNA fragmentation in mammalian cells.
我们在此描述了迄今已鉴定出的人类脱氧核糖核酸酶I家族脱氧核糖核酸酶，即脱氧核糖核酸酶I、脱氧核糖核酸酶X、脱氧核糖核酸酶γ和DNAS1L2的特性。发现脱氧核糖核酸酶I家族基因具有不同的组织特异性表达，并提示其发挥独特的生理作用。所有重组脱氧核糖核酸酶均显示为Ca(2+)/Mg(2+)-依赖性核酸内切酶，催化DNA水解产生3'-OH/5'-P末端。在中性条件下观察到脱氧核糖核酸酶I、脱氧核糖核酸酶X和脱氧核糖核酸酶γ具有高活性，而DNAS1L2在酸性pH下显示出最大活性。这些酶还具有一些其他特性：观察到它们对G-肌动蛋白、金精三羧酸和金属离子的敏感性不同。利用HeLa S3细胞中的瞬时表达系统，研究了脱氧核糖核酸酶在细胞凋亡中的可能作用。每种脱氧核糖核酸酶的异位表达对宿主细胞没有毒性作用；然而，仅在诱导细胞凋亡后，在转染了脱氧核糖核酸酶γ的细胞中观察到广泛的DNA片段化。此外，脱氧核糖核酸酶γ在活细胞中定位于核周区域，并在细胞凋亡期间转位至细胞核。我们的结果表明，脱氧核糖核酸酶I、脱氧核糖核酸酶X、脱氧核糖核酸酶γ和DNAS1L2具有相似但独特的核酸内切酶活性，并且在脱氧核糖核酸酶I家族脱氧核糖核酸酶中，脱氧核糖核酸酶γ能够在哺乳动物细胞中产生凋亡性DNA片段化。
