Chang Yue, Feng Li-Fang, Xiong Jie, Miao Wei
State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, the Chinese Academy of Sciences, Wuhan 430072, China.
Dongwuxue Yanjiu. 2011 Oct;32(5):476-84. doi: 10.3724/SP.J.1141.2011.05476.
Tetrahymena has a high genetic polymorphism of metallothionein proteins. These protein isoforms can be divided into subfamilies 7a and 7b. We used real-time quantitative PCR to test the expression levels of Tetrahymena thermophila metallothionein genes MTT2 and MTT4 after exposure to different inducers, including Hg, Cu, Cd, Zn and H(2)O(2). Both genes were most efficiently induced by Cu and secondly by Hg. Their expression was slightly up-regulated after exposure to Cd and Zn, but down-regulated by H(2)O(2). The expression pattern differed from those reported in the 7a subfamily, but was consistent with 7b subfamily members. However, the induced expression level of MTT4 was much higher than that of MTT2, which might be due to differences in their upstream regulatory elements (AP-1, MRE). The high similarities in gene structures and functions indicate that MTT2 and MTT4 were generated by recent gene duplication following the dosage balance model.
嗜热四膜虫的金属硫蛋白具有高度的遗传多态性。这些蛋白质异构体可分为7a和7b亚家族。我们使用实时定量PCR检测了嗜热四膜虫金属硫蛋白基因MTT2和MTT4在暴露于不同诱导剂（包括汞、铜、镉、锌和过氧化氢）后的表达水平。这两个基因最有效的诱导剂是铜，其次是汞。暴露于镉和锌后它们的表达略有上调，但过氧化氢使其下调。这种表达模式与7a亚家族中报道的不同，但与7b亚家族成员一致。然而，MTT4的诱导表达水平远高于MTT2，这可能是由于它们上游调控元件（AP-1、MRE）的差异。基因结构和功能的高度相似表明MTT2和MTT4是根据剂量平衡模型通过近期基因复制产生的。
