【摘要】 对烟草(Nicotiana tobacum)rbcL转录单位3’端前后相连的2个逆向重复序列作系统删减并单独将此2个序列分开。在原校体系中考察这些缺失子的转录物,结果表明,成熟rbcL mRNA的积累依赖于3’端的大逆向重复序列及未翻译区的一段序列。 将带有逆向重复序列的片段插入菠菜rbcL启动子及苏氨酸终止子之间,大肠杆菌的RNA多聚酶读过rbcL3’端的逆向重复序列而全部停止在苏氨酸终止子的终止位点,表明成熟的rbcL mRNA不是rbcL转录的直接产物,而是由前体mRNA经转录后的加工过程后形成的。更多还原

【Abstract】 There is a 15bp large reverse repeated sequence proceeded by a 7bp small one in the 3’flan-king region of rbcL of Nicotiana tabacum. A 383 bp of Xbal fragment containing these tandem-ly repeats was inserted into the plasmid pXSA, ai the position between the λp and the cat gene. Then these two repeats were separated and deleted systematically to obtain various deletions. The deletion pRT65, pRT74 and.pRT83 was sequenced to determine the deleted base pairs exactly.S1 mapping analysis was adopted to investigate the transcripts of these deletions in E. coli JM83. The results showed us that the stability of mature 306bp mRNA relied on the large repeat and a short sequence downstream. The small one was not efficient.The regulation level of the rbcL termination was also investigated. The Xbal-EcoRI fragments from pRT65, pRT74 and pRT83 were transferred into pSP-TT at the position between the spinach promoter and threonine terminator to construct pRT65, pRT74 and pRT83 respectively. The results from SI mapping analysis showed that the E. coli RNA polymerase read through the 3’ flanking region of rboL gene and terminated at the stop site of threonine terminator. These results suggested that mature rbcL mRNA might be the product precisely processed from a precursor mRNA and the 3’ flanking sequence might be the signal for precursor mRNA to be processed to the correct position.更多还原