先前科学家们认为，动物和植物细胞死亡的遗传学过程是不同的。现在，一国际研究团队发现，植物和动物中决定细胞程序性死亡的遗传学过程实际上是进化相关的，并且用相同的方式执行功能。

这项研究结果发布在10月11日的Nature Cell Biology上。

对于植物、动物，以及人类来说，细胞的生长和死亡同样都受到严格控制。这些过程中，细胞死亡是以程序性细胞死亡的形式进行的。该过程的破坏会导致严重疾病的发生，比如癌症，帕金森氏症。

动物细胞的蛋白酶属于一个叫caspases的蛋白家族，而植物中没有caspases，取而代之的是meta-caspases，其被认为是caspases的祖先，能降解TUDOR-SN。

科学家首次证实蛋白TUDOR-SN是被一种类似的蛋白激酶所降解的，而这种蛋白激酶在植物和动物细胞中都存在。因此研究人员在植物和动物之间发现了一个进一步的关联。这项研究结果将对未来这类重要的蛋白家族的研究产生重要影响。

研究人员表示，缺少TUDOR-SN的细胞经常会出现过早的细胞程序性死亡。此外，有机物水平的植物功能研究表明TUDOR-SN对晶胚和花粉的发育是必须的。因此，TUDOR-SN对阻止细胞程序性死亡来说是很重要的。

原始出处：

Nature Cell Biology 11 October 2009 | doi:10.1038/ncb1979

Tudor staphylococcal nuclease is an evolutionarily conserved component of the programmed cell death degradome

Jens F. Sundstr?m1,9, Alena Vaculova2,9, Andrei P. Smertenko3,9, Eugene I. Savenkov1,9, Anna Golovko1,9, Elena Minina1,9, Budhi S. Tiwari1, Salvador Rodriguez-Nieto2, Andrey A. Zamyatnin, Jr1, Tuuli V?lineva4, Juha Saarikettu4, Mikko J. Frilander5, Maria F. Suarez6, Anton Zavialov7, Ulf St?hl1, Patrick J. Hussey3, Olli Silvennoinen4,8, Eva Sundberg1, Boris Zhivotovsky2 & Peter V. Bozhkov1

Programmed cell death (PCD) is executed by proteases, which cleave diverse proteins thus modulating their biochemical and cellular functions. Proteases of the caspase family and hundreds of caspase substrates constitute a major part of the PCD degradome in animals1, 2. Plants lack close homologues of caspases, but instead possess an ancestral family of cysteine proteases, metacaspases3, 4. Although metacaspases are essential for PCD5, 6, 7, their natural substrates remain unknown4, 8. Here we show that metacaspase mcII-Pa cleaves a phylogenetically conserved protein, TSN (Tudor staphylococcal nuclease), during both developmental and stress-induced PCD. TSN knockdown leads to activation of ectopic cell death during reproduction, impairing plant fertility. Surprisingly, human TSN (also known as p100 or SND1), a multifunctional regulator of gene expression9, 10, 11, 12, 13, 14, 15, is cleaved by caspase-3 during apoptosis. This cleavage impairs the ability of TSN to activate mRNA splicing, inhibits its ribonuclease activity and is important for the execution of apoptosis. Our results establish TSN as the first biological substrate of metacaspase and demonstrate that despite the divergence of plants and animals from a common ancestor about one billion years ago and their use of distinct PCD pathways, both have retained a common mechanism to compromise cell viability through the cleavage of the same substrate, TSN.

1 Department of Plant Biology and Forest Genetics, Uppsala BioCenter, Swedish University of Agricultural Sciences, Box 7080, SE-75007 Uppsala, Sweden.
2 Institute of Environmental Medicine, Karolinska Institutet, Box 210, SE-17177, Stockholm, Sweden.
3 The Integrative Cell Biology Laboratory, School of Biological and Biomedical Sciences, University of Durham, South Road, Durham DH1 3LE, UK.
4 Institute of Medical Technology, University of Tampere, FIN-33014 Tampere, Finland.
5 Institute of Biotechnology, University of Helsinki, FIN-00014 Helsinki, Finland.
6 Departamento de Biologia Molecular y Bioquimica, Facultad de Ciencias, Universidad de Malaga, Campus de Teatinos, 29071 Malaga, Spain.
7 Department of Molecular Biology, Biomedical Center, Swedish University of Agricultural Sciences, Box 590, SE-75124 Uppsala, Sweden.
8 Department of Clinical Microbiology, Tampere University Hospital, FIN-33520 Tampere, Finland.
9 These authors contributed equally to this work.