Lloubès R, Baty D, Lazdunski C
Centre de Biochimie et de Biologie Moléculaire du Centre National de la Recherche Scientifique, Marseille, France.
Nucleic Acids Res. 1988 May 11;16(9):3739-49. doi: 10.1093/nar/16.9.3739.
We have analysed by S1 nuclease mapping the in vivo termination sites of transcription of the caa-cal operon and cai gene. The termination region for caa mRNA (T1A terminator) features characteristics of a rho-independent terminator. This terminator is a convergent transcription terminator, its complementary secondary structure being present at the 3'-end of cai mRNA. The caa-cal mRNA terminator (T2A terminator) has a stable potential secondary structure and shows homology with rho-dependent terminators. In vitro transcription of caa-cal operon demonstrated that the two terminators T1A and T2A are efficient. The 3'-ends of the mRNAs which end at T1A and T2A were analysed by S1 mapping with total RNA purified from a mutant strain deficient in exoribonuclease activities, in particular RNase II. The results suggest that the potential secondary structures of T1A and T2A are sufficiently stable to prevent 3'-end degradation by RNase II. On the other hand, the T2A terminator should be efficient enough to stop transcription through the downstream DNA region involved in pColA replication.
我们通过S1核酸酶图谱分析了caa - cal操纵子和cai基因转录的体内终止位点。caa mRNA的终止区域（T1A终止子）具有不依赖ρ因子的终止子特征。该终止子是一个收敛转录终止子，其互补二级结构存在于cai mRNA的3'端。caa - cal mRNA终止子（T2A终止子）具有稳定的潜在二级结构，并与依赖ρ因子的终止子显示出同源性。caa - cal操纵子的体外转录表明，两个终止子T1A和T2A是有效的。通过用从缺乏外切核糖核酸酶活性，特别是RNase II的突变菌株中纯化的总RNA进行S1图谱分析，对在T1A和T2A处终止的mRNA的3'端进行了分析。结果表明，T1A和T2A的潜在二级结构足够稳定，以防止被RNase II进行3'端降解。另一方面，T2A终止子应该足够有效，以阻止通过参与pColA复制的下游DNA区域进行转录。
