Vera A, Matsubayashi T, Sugiura M
Center for Gene Research, Nagoya University, Japan.
Mol Gen Genet. 1992 May;233(1-2):151-6. doi: 10.1007/BF00587573.
A new transcription unit has been identified and characterized in the small single-copy region of tobacco chloroplast DNA. A primary transcript (1550 nucleotides) spanning the entire transcription unit contains no significant open reading frames (ORFs), other than ORF55, recently identified as the gene encoding the ribosomal protein CL32 (rpl32). The leader sequence extends 1101 nucleotides from the rpl32 initiation codon. Primer extension and in vitro capping experiments in combination with ribonuclease protection assays, revealed a promoter situated more than 322 bp inside the coding region of ndhF, which is divergently oriented with respect to rpl32. A canonical Pribnow-box is found just upstream of the transcription start site, but a typical -35 motif was not detected. This is the first internal divergent promoter to be characterized in the chloroplast genome.
在烟草叶绿体DNA的小单拷贝区域中，一个新的转录单元已被鉴定和表征。一个跨越整个转录单元的初级转录本（1550个核苷酸），除了最近被鉴定为编码核糖体蛋白CL32（rpl32）的基因ORF55外，没有明显的开放阅读框（ORF）。前导序列从rpl32起始密码子延伸1101个核苷酸。引物延伸和体外加帽实验与核糖核酸酶保护分析相结合，揭示了一个位于ndhF编码区域内超过322 bp处的启动子，它与rpl32的方向相反。在转录起始位点上游正好发现了一个典型的Pribnow框，但未检测到典型的-35基序。这是叶绿体基因组中第一个被表征的内部反向启动子。
