Functional specialization of Chlamydomonas reinhardtii cytosolic thioredoxin h1 in the response to alkylation-induced DNA damage.
Functional specialization of Chlamydomonas reinhardtii cytosolic thioredoxin h1 in the response to alkylation-induced DNA damage.
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莱茵衣藻胞质硫氧还蛋白 h1 在响应烷基化诱导的 DNA 损伤中的功能特化。
DOI：
10.1128/ec.4.2.262-273.2005
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发表时间：
2005
期刊：
影响因子：
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通讯作者：
Cerutti,Heriberto
中科院分区：
文献类型：
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作者：
Sarkar,Nandita;Lemaire,Stephane;Wu-Scharf,Danxia;Issakidis-Bourguet,Emmanuelle;Cerutti,Heriberto
DNA损伤是固有的细胞过程的副产品，如DNA复制，或者是暴露在遗传毒性物质中的结果。生物体已经进化出多种机制来避免、耐受或修复DNA损伤。为了深入了解这些过程，我们在绿藻莱茵衣藻中分离了对DNA损伤剂高度敏感的突变体。突变株Ble-1在用甲基磺酸甲酯(MMS)、博莱霉素或过氧化氢(H_2O_2)处理时存活率降低，但在紫外线照射下表现出与野生型相似的表现。BLE-1携带广泛的染色体缺失，其中包括编码胞浆硫氧还蛋白H1(Trxh1)的基因。用Trxh1的野生型拷贝转化Ble-1，完全纠正了MMS的过敏性，部分恢复了对博莱霉素的耐受性。Trxh1还弥补了MMS引起的DNA链断裂和碱不稳定部位的修复缺陷。此外，Trxh1-β-葡萄糖醛酸苷酶融合蛋白被转移到细胞核以响应MMS的处理。然而，有些令人惊讶的是，Trxh1未能纠正Ble-1对过氧化氢的过敏性。此外，在野生型菌株中，通过RNA干扰抑制Trxh1可以增强对MMS和DNA修复缺陷的敏感性，但不会增加对过氧化氢的细胞毒性。硫氧还蛋白与许多生物体的氧化应激反应有关。然而，我们的结果表明，衣藻酶Trxh1在MMS诱导的DNA损伤的修复中具有特定的作用，而对于对H_2O_2的反应来说，它是必不可少的。这些观察还表明，由于另一种衣藻亚型(Trxh2)不能弥补Trxh1的缺失，细胞内硫氧还蛋白之间的功能专化。
DNA damage occurs as a by-product of intrinsic cellular processes, like DNA replication, or as a consequence of exposure to genotoxic agents. Organisms have evolved multiple mechanisms to avoid, tolerate, or repair DNA lesions. To gain insight into these processes, we have isolated mutants hypersensitive to DNA-damaging agents in the green algaChlamydomonas reinhardtii. One mutant, Ble-1, showed decreased survival when it was treated with methyl methanesulfonate (MMS), bleomycin, or hydrogen peroxide (H2O2) but behaved like the wild type when it was exposed to UVC irradiation. Ble-1 carries an extensive chromosomal deletion that includes the gene encoding cytosolic thioredoxin h1 (Trxh1). Transformation of Ble-1 with a wild-type copy ofTrxh1fully corrected the MMS hypersensitivity and partly restored the tolerance to bleomycin.Trxh1also complemented a defect in the repair of MMS-induced DNA strand breaks and alkali-labile sites. In addition, a Trxh1-β-glucuronidase fusion protein translocated to the nucleus in response to treatment with MMS. However, somewhat surprisingly,Trxh1failed to correct the Ble-1 hypersensitivity to H2O2. Moreover,Trxh1suppression by RNA interference in a wild-type strain resulted in enhanced sensitivity to MMS and DNA repair defects but no increased cytotoxicity to H2O2. Thioredoxins have been implicated in oxidative-stress responses in many organisms. Yet our results indicate a specific role ofChlamydomonasTrxh1 in the repair of MMS-induced DNA damage, whereas it is dispensable for the response to H2O2. These observations also suggest functional specialization among cytosolic thioredoxins since anotherChlamydomonasisoform (Trxh2) does not compensate for the lack of Trxh1.