Zerges W, Rochaix J D
Department of Molecular Biology, University of Geneva, Switzerland.
Mol Cell Biol. 1994 Aug;14(8):5268-77. doi: 10.1128/mcb.14.8.5268-5277.1994.
In the green alga Chlamydomonas reinhardtii, the nuclear mutations F34 and F64 have been previously shown to abolish the synthesis of the photosystem II core polypeptide subunit P6, which is encoded by the chloroplast psbC gene. In this report the functions encoded by F34 and F64 are shown to be required for translation of the psbC mRNA, on the basis of the finding that the expression of a heterologous reporter gene fused to the psbC 5' nontranslated leader sequence requires wild-type F34 and F64 alleles in vivo. Moreover, a point mutation in the psbC 5' nontranslated leader sequence suppresses this requirement for wild-type F34 function. In vitro RNA-protein cross-linking studies reveal that chloroplast protein extracts from strains carrying the F64 mutation contain an approximately 46-kDa RNA-binding protein. The absence of the RNA-binding activity of this protein in chloroplast extracts of wild-type strains suggests that it is related to the role of the F64-encoded function for psbC mRNA translation. The binding specificity of this protein appears to be for an AU-rich RNA sequence motif.
在绿藻莱茵衣藻中，核突变F34和F64先前已被证明会消除光系统II核心多肽亚基P6的合成，该亚基由叶绿体psbC基因编码。在本报告中，基于以下发现表明F34和F64编码的功能是psbC mRNA翻译所必需的：与psbC 5'非翻译前导序列融合的异源报告基因的表达在体内需要野生型F34和F64等位基因。此外，psbC 5'非翻译前导序列中的一个点突变抑制了对野生型F34功能的这种需求。体外RNA-蛋白质交联研究表明，携带F64突变的菌株的叶绿体蛋白提取物含有一种约46 kDa的RNA结合蛋白。野生型菌株的叶绿体提取物中该蛋白缺乏RNA结合活性，这表明它与F64编码的功能对psbC mRNA翻译的作用有关。该蛋白的结合特异性似乎针对富含AU的RNA序列基序。
