A nuclear gene of Chlamydomonas reinhardtii, Tba1, encodes a putative oxidoreductase required for translation of the chloroplast psbA mRNA.
A nuclear gene of Chlamydomonas reinhardtii, Tba1, encodes a putative oxidoreductase required for translation of the chloroplast psbA mRNA.
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DOI：
10.1111/j.1365-313x.2005.02378.x
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发表时间：
2005-03
期刊：
影响因子：
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通讯作者：
A. Somanchi;D. Barnes;S. Mayfield
中科院分区：
文献类型：
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作者：
A. Somanchi;D. Barnes;S. Mayfield
叶绿体蛋白质的生物合成在很大程度上是转录后调节的，并且已经鉴定了许多核编码的基因，这些基因是特定叶绿体mRNA的翻译或稳定性所需的。莱茵衣藻的核突变体hf 261，psbA mRNA翻译缺陷，psbA mRNA与核糖体的结合减少，并且叶绿体定位的多聚腺苷酸结合蛋白（cPAB 1）与psbA mRNA的结合缺陷。克隆的hf261基因座和互补的hf261使用野生型基因组克隆已确定了一个新的基因，Tba1，psbA的翻译效应子。补充了wt Tba1基因的菌株恢复了psbA mRNA与核糖体结合的能力，并恢复了cPAB1对psbA mRNA的RNA结合活性。Tba1基因的分析鉴定了与氧化还原酶具有显著同源性的蛋白质。Tba1表达对cPAB1的RNA结合活性以及对psbA mRNA与核糖体的结合的影响表明，Tba1作为cPAB1 RNA结合活性的氧化还原调节剂，间接促进psbA mRNA翻译起始。叶绿体翻译纳入Tba1和其他成员的psbA mRNA结合复合物的模型。
Biosynthesis of chloroplast proteins is to a large extent regulated post-transcriptionally, and a number of nuclear-encoded genes have been identified that are required for translation or stability of specific chloroplast mRNAs. A nuclear mutant of Chlamydomonas reinhardtii, hf261, deficient in the translation of the psbA mRNA, has reduced association of the psbA mRNA with ribosomes and is deficient in binding of the chloroplast localized poly (A) binding protein (cPAB1) to the psbA mRNA. Cloning of the hf261 locus and complementation of hf261 using a wt genomic clone has identified a novel gene, Tba1, for translational affector of psbA. Strains complemented with the wt Tba1 gene restore the ability of the psbA mRNA to associate with ribosomes, and restores RNA binding activity of cPAB1 for the psbA mRNA. Analysis of the Tba1 gene identified a protein with significant homology to oxidoreductases. The effect of Tba1 expression on the RNA binding activity of cPAB1, and on the association of psbA mRNA with ribosomes, implies that Tba1 functions as a redox regulator of cPAB1 RNA binding activity to indirectly promote psbA mRNA translation initiation. A model of chloroplast translation incorporating Tba1 and other members of the psbA mRNA binding complex is presented.