van Wezel G P, Krab I M, Douthwaite S, Bibb M J, Vijgenboom E, Bosch L
Leiden University, Department of Biochemistry, The Netherlands.
Microbiology (Reading). 1994 Dec;140 ( Pt 12):3357-65. doi: 10.1099/13500872-140-12-3357.
Transcription start sites and processing sites of the Streptomyces coelicolor A3(2) rrnA operon have been investigated by a combination of in vivo and in vitro transcription analyses. The data from these approaches are consistent with the existence of four in vivo transcription sites, corresponding to the promoters P1-P4. The transcription start sites are located at -597, -416, -334 and -254 relative to the start of the 16S rRNA gene. Two putative processing sites were identified, one of which is similar to a sequence reported earlier in S. coelicolor and other eubacteria. The P1 promoter is likely to be recognized by the RNA polymerase holoenzyme containing sigma hrdB, the principal sigma factor in S. coelicolor. P2 also shares homology with the consensus for vegetative promoters, but has a sequence overlapping the consensus -35 region that is also present in the -35 regions of P3 and P4. The -35 sequence common to P2, P3 and P4 is not similar to any other known consensus promoter sequence. In fast-growing mycelium, P2 appears to be the most frequently used promoter. Transcription from all of the rrnA promoters decreased during the transition from exponential to stationary phase, although transcription from P1 and P2 ceased several hours before that from P3 and P4.
通过体内和体外转录分析相结合的方法，对天蓝色链霉菌A3(2) rrnA操纵子的转录起始位点和加工位点进行了研究。这些方法得到的数据与四个体内转录位点的存在相一致，对应于启动子P1 - P4。转录起始位点相对于16S rRNA基因的起始位置分别位于-597、-416、-334和-254处。鉴定出了两个推定的加工位点，其中一个与先前在天蓝色链霉菌和其他真细菌中报道的序列相似。P1启动子可能被含有σhrdB的RNA聚合酶全酶识别，σhrdB是天蓝色链霉菌中的主要σ因子。P2也与营养型启动子的共有序列具有同源性，但有一个序列与共有-35区域重叠，该区域也存在于P3和P4的-35区域中。P2、P3和P4共有的-35序列与任何其他已知的共有启动子序列都不相似。在快速生长的菌丝体中，P2似乎是最常用的启动子。从指数生长期到稳定期的转变过程中，所有rrnA启动子的转录都减少了，尽管P1和P2的转录比P3和P4提前几个小时停止。
