[The correlation between the maturation of rbcL transcripts and its flanking sequence in a prokaryotic system]

There is a 15bp large reverse repeated sequence proceeded by a 7bp small one in the 3'flanking region of rbcL of Nicotiana tabacum. A 383 bp of XbaI fragment containing these tandemly repeats was inserted into the plasmid p lambda S delta, at the position between the lambda p 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 XbaI-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 S1 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.