Ebbole D J, Zalkin H
Department of Biochemistry, Purdue University, West Lafayette, Indiana 47907.
J Biol Chem. 1988 Aug 5;263(22):10894-902.
Transcription of the Bacillus subtilis pur operon is regulated independently by adenine and guanine nucleotides (Ebbole, D. J., and Zalkin, H. (1987) J. Biol. Chem. 262, 8274-8287). Guanine nucleotides regulate transcription by a termination-antitermination mechanism in a 242-nucleotide, 5'-untranslated mRNA leader region. We have identified an apparently intact, terminated transcript of approximately 200 nucleotides in length, having a half-life of about 0.7 min. The terminated transcript is degraded in a series of discrete steps resulting in the accumulation of stable intermediates in vivo. We have used Northern blot analysis, primer extension, and nuclease S1 mapping to align the degradation intermediates with the nucleotide sequence and assign secondary structures that may contribute to the stability of the intermediates. Degradation is initiated by endonucleolytic cleavage of the approximately 200-nucleotide terminated transcript generating approximately 93- and approximately 97-nucleotide 5' and 3' moieties, respectively. The approximately 93-nucleotide 5' and approximately 97-nucleotide 3' intermediates are further degraded to approximately 88 and approximately 58 nucleotides, respectively. The 5'-end of pur operon mRNA and the attenuated transcript are degraded by different pathways.
枯草芽孢杆菌嘌呤操纵子的转录由腺嘌呤和鸟嘌呤核苷酸独立调控（埃博尔，D. J.，和扎尔金，H.（1987年）《生物化学杂志》262卷，8274 - 8287页）。鸟嘌呤核苷酸通过一种终止 - 抗终止机制在一个242个核苷酸的5' - 非翻译mRNA前导区域调控转录。我们鉴定出了一种长度约为200个核苷酸的明显完整的终止转录本，其半衰期约为0.7分钟。该终止转录本在一系列离散步骤中被降解，导致体内稳定中间体的积累。我们利用Northern印迹分析、引物延伸和核酸酶S1作图将降解中间体与核苷酸序列比对，并确定可能有助于中间体稳定性的二级结构。降解由大约200个核苷酸的终止转录本的内切核酸酶切割引发，分别产生大约93个核苷酸和大约97个核苷酸的5'和3'部分。大约93个核苷酸的5'中间体和大约97个核苷酸的3'中间体进一步分别降解为大约88个核苷酸和大约58个核苷酸。嘌呤操纵子mRNA的5'末端和衰减转录本通过不同途径降解。
