Kurepa Jasmina, Walker Joseph M, Smalle Jan, Gosink Mark M, Davis Seth J, Durham Tessa L, Sung Dong-Yul, Vierstra Richard D
Cellular and Molecular Biology Program and the Department of Horticulture, University of Wisconsin, Madison, Wisconsin 53706, USA.
J Biol Chem. 2003 Feb 28;278(9):6862-72. doi: 10.1074/jbc.M209694200. Epub 2002 Dec 12.
Small ubiquitin-like modifier (SUMO) is a member of the superfamily of ubiquitin-like polypeptides that become covalently attached to various intracellular target proteins as a way to alter their function, location, and/or half-life. Here we show that the SUMO conjugation system operates in plants through a characterization of the Arabidopsis SUMO pathway. An eight-gene family encoding the SUMO tag was discovered as were genes encoding the various enzymes required for SUMO processing, ligation, and release. A diverse array of conjugates could be detected, some of which appear to be SUMO isoform-specific. The levels of SUMO1 and -2 conjugates but not SUMO3 conjugates increased substantially following exposure of seedlings to stress conditions, including heat shock, H(2)O(2), ethanol, and the amino acid analog canavanine. The heat-induced accumulation could be detected within 2 min from the start of a temperature upshift, suggesting that SUMO1/2 conjugation is one of the early plant responses to heat stress. Overexpression of SUMO2 enhanced both the steady state levels of SUMO2 conjugates under normal growth conditions and the subsequent heat shock-induced accumulation. This accumulation was dampened in an Arabidopsis line engineered for increased thermotolerance by overexpressing the cytosolic isoform of the HSP70 chaperonin. Taken together, the SUMO conjugation system appears to be a complex and functionally heterogeneous pathway for protein modification in plants with initial data indicating that one important function may be in stress protection and/or repair.
小泛素样修饰物（SUMO）是泛素样多肽超家族的成员，它以共价方式附着于各种细胞内靶蛋白，从而改变其功能、定位和/或半衰期。在此，我们通过对拟南芥SUMO途径的表征表明，SUMO缀合系统在植物中发挥作用。我们发现了一个由八个基因组成的家族，该家族编码SUMO标签，同时还发现了编码SUMO加工、连接和释放所需各种酶的基因。可以检测到一系列不同的缀合物，其中一些似乎是SUMO异构体特异性的。在幼苗暴露于热休克、H₂O₂、乙醇和氨基酸类似物刀豆氨酸等胁迫条件下后，SUMO1和-2缀合物的水平大幅增加，但SUMO3缀合物的水平没有增加。从温度升高开始2分钟内就能检测到热诱导的积累，这表明SUMO1/2缀合是植物对热胁迫的早期反应之一。SUMO2的过表达在正常生长条件下提高了SUMO2缀合物的稳态水平，以及随后热休克诱导的积累。在通过过表达HSP70伴侣蛋白的胞质异构体而设计的耐热性增强的拟南芥品系中，这种积累受到了抑制。综上所述，SUMO缀合系统似乎是植物中一种复杂且功能异质的蛋白质修饰途径，初步数据表明其一个重要功能可能在于胁迫保护和/或修复。
