Yao W B, Meng B Y, Tanaka M, Sugiura M
Center for Gene Research, Nagoya University, Japan.
Nucleic Acids Res. 1989 Dec 11;17(23):9583-91. doi: 10.1093/nar/17.23.9583.
Transcription of the psbD-psbC gene cluster in tobacco chloroplasts has been studied. This cluster contains in linear sequence the overlapping genes encoding the D2 and 43 kDa proteins of Photosystem II (psbD and psbC, respectively), and ORF62. Eight major transcripts ranging from 1.5 to 4.4 kb were detected by northern blot analysis. S1 mapping experiments revealed that these multiple transcripts comprise five distinct 5' ends whose precise positions were further determined by primer extension analysis. Two of the five 5' ends were determined to be the transcriptional initiation sites by in vitro capping assays: the main site is located 905 bp upstream from the ATG codon of psbD and the additional site is 194 bp upstream from the first ATG codon of psbC. The latter site and the preceding prokaryotic promoter motif are within the protein-coding region of psbD. The 3' ends of transcripts were determined by S1 mapping.
对烟草叶绿体中psbD-psbC基因簇的转录进行了研究。该基因簇按线性顺序包含编码光系统II的D2和43 kDa蛋白（分别为psbD和psbC）以及开放阅读框62的重叠基因。通过Northern印迹分析检测到8种主要转录本，大小从1.5到4.4 kb不等。S1图谱实验表明，这些多个转录本包含5个不同的5'末端，其精确位置通过引物延伸分析进一步确定。通过体外加帽试验确定这5个5'末端中的两个为转录起始位点：主要位点位于psbD的ATG密码子上游905 bp处，另一个位点位于psbC的第一个ATG密码子上游194 bp处。后一个位点和前面的原核启动子基序位于psbD的蛋白质编码区内。转录本的3'末端通过S1图谱确定。
