Machado C R, de Oliveira R L, Boiteux S, Praekelt U M, Meacock P A, Menck C F
Depto. de Biologia, Universidade de São Paulo, Brazil.
Plant Mol Biol. 1996 Jun;31(3):585-93. doi: 10.1007/BF00042231.
An Arabidopsis thaliana cDNA was isolated by complementation of the Escherichia coli mutant strain BW535 (xth, nfo, nth), which is defective in DNA base excision repair pathways. This cDNA partially complements the methyl methane sulfonate (MMS) sensitive phenotype of BW535. It also partially corrects the UV-sensitive phenotype of E. coli AB1886 (uvrA) and restores its ability to reactivate UV-irradiated lambda phage. It has an insert of ca. 1.3 kb with an open reading frame of 1047 bp (predicting a protein with a molecular mass of 36 kDa). This cDNA presents a high homology to a stress related gene from two species of Fusarium (sti35) and to genes whose products participate in the thiamine biosynthesis pathway, THI4, from Saccharomyces cerevisiae and nmt2 from Schizosaccharomyces pombe. The Arabidopsis predicted polypeptide has homology to several protein motifs: amino-terminal chloroplast transit peptide, dinucleotide binding site, DNA binding and bacterial DNA polymerases. The auxotrophy for thiamine in the yeast thi4::URA3 disruption strain is complemented by the Arabidopsis gene. Thus, the cloned gene, named thi1, is likely to function in the biosynthesis of thiamine in plants. The data presented in this work indicate that thi1 may also be involved in DNA damage tolerance in plant cells.
通过对大肠杆菌突变株BW535（xth、nfo、nth）进行互补，分离出了拟南芥cDNA，该突变株在DNA碱基切除修复途径中存在缺陷。此cDNA部分互补了BW535对甲磺酸甲酯（MMS）敏感的表型。它还部分纠正了大肠杆菌AB1886（uvrA）对紫外线敏感的表型，并恢复了其重新激活紫外线照射的λ噬菌体的能力。它有一个约1.3 kb的插入片段，开放阅读框为1047 bp（预测编码一个分子量为36 kDa的蛋白质）。该cDNA与两种镰刀菌的一个胁迫相关基因（sti35）以及酿酒酵母的THI4和粟酒裂殖酵母的nmt2等参与硫胺素生物合成途径的基因具有高度同源性。拟南芥预测的多肽与几个蛋白质基序具有同源性：氨基末端叶绿体转运肽、二核苷酸结合位点、DNA结合以及细菌DNA聚合酶。酵母thi4::URA3缺失菌株对硫胺素的营养缺陷型由拟南芥基因互补。因此，克隆的基因thi1可能在植物硫胺素的生物合成中发挥作用。这项工作中呈现的数据表明，thi1也可能参与植物细胞对DNA损伤的耐受性。
