Department of Molecular Genetics, Centre for Research in Agricultural Genomics CRAG (CSIC-IRTA-UAB-UB), Campus UAB, Bellaterra (Cerdanyola del Vallès), 08193 Barcelona, Spain.
BMC Plant Biol. 2013 Nov 20;13:186. doi: 10.1186/1471-2229-13-186.
Camptothecin is a plant alkaloid that specifically binds topoisomerase I, inhibiting its activity and inducing double stranded breaks in DNA and activating the cell responses to DNA damage.
Maize cultured cells were incubated in the presence of different concentrations of camptothecin. Camptothecin inhibits cultured cell growth, induces genomic DNA degradation, and induces a 32 kDa Ca2+/Mg2+-dependent nuclease activity. This nuclease, we called CaMNUC32, is inhibited by Zn2+ and by acid pH, it is mainly localized in the nucleus and it cleaves single- and double-stranded DNA, with a higher activity against single-stranded DNA. Two-dimensional electrophoresis combined with mass spectrometry suggests that CaMNUC32 is a member of the type I S1/P1 nuclease family. This type of nucleases are usually Zn2+-dependent but our results support previous indications that S1-type nucleases have a wide variety of enzyme activities, including Ca2+/Mg2+-dependent.
We have identified and characterized CaMNUC32, a 32 kDa Ca2+/Mg2+-dependent nuclease of the S1/P1 family induced by the topoisomerase I inhibitor camptothecin in maize cultured cells.
喜树碱是一种植物生物碱，它特异性地与拓扑异构酶 I 结合，抑制其活性并诱导 DNA 双链断裂，激活细胞对 DNA 损伤的反应。
用不同浓度的喜树碱孵育玉米培养细胞。喜树碱抑制培养细胞生长，诱导基因组 DNA 降解，并诱导 32 kDa Ca2+/Mg2+-依赖性核酸内切酶活性。我们将这种核酸内切酶称为 CaMNUC32，它被 Zn2+抑制，被酸性 pH 抑制，主要定位于核内，可切割单链和双链 DNA，对单链 DNA 的活性更高。二维电泳结合质谱分析表明，CaMNUC32 是 I 型 S1/P1 核酸内切酶家族的成员。这种核酸内切酶通常依赖 Zn2+，但我们的结果支持先前的研究结果，即 S1 型核酸内切酶具有多种酶活性，包括 Ca2+/Mg2+-依赖性。
我们已经鉴定并表征了 CaMNUC32，这是一种在玉米培养细胞中由拓扑异构酶 I 抑制剂喜树碱诱导的 32 kDa Ca2+/Mg2+-依赖性 S1/P1 家族核酸内切酶。
