Dhaese P, De Greve H, Gielen J, Seurinck L, Van Montagu M, Schell J
Laboratorium voor Genetica, Rijksuniversiteit Gent, Belgium.
EMBO J. 1983;2(3):419-26. doi: 10.1002/j.1460-2075.1983.tb01439.x.
Sequences in the 3'-untranslated region of two different octopine T-DNA genes were analyzed with regard to their significance in polyadenylation. Poly(A) addition sites were localized precisely by S1 nuclease mapping with T-DNA-derived mRNAs isolated from tobacco. The gene encoding transcript 7' contains two AATAAA hexanucleotides, respectively 119 bp and 170 bp downstream of the TAA stop codon. A single poly(A) site was mapped 24-25 bp downstream of the first AATAAA. Further, we show that a mutant octopine synthase gene, which has lost part of its 3'-untranslated region by deletion, is still active. This mutant gene terminates 19 bp upstream from the major wild-type polyadenylation site. The deletion also removes the AATAAT signal preceding this site. The mutant octopine synthase gene contains a minimum of four different poly(A) sites. The most prominent of these sites is identical to the minor poly(A) site of the wild-type gene, and is preceded by a sequence AATGAATATA. Three other sites are located within the adjacent plant DNA, giving rise to hybrid T-DNA/plant DNA transcripts. The two most distal sites are probably dependent on a motif AATAAATAAA, found 29 bp away from the T-DNA/plant DNA junction.
对两种不同章鱼碱T-DNA基因3'-非翻译区的序列进行了分析，以研究它们在多聚腺苷酸化中的意义。通过用从烟草中分离的T-DNA衍生的mRNA进行S1核酸酶图谱分析，精确地定位了多聚（A）添加位点。编码转录本7'的基因在TAA终止密码子下游分别含有两个AATAAA六核苷酸，距离分别为119 bp和170 bp。在第一个AATAAA下游24 - 25 bp处定位了一个单一的多聚（A）位点。此外，我们表明，一个突变的章鱼碱合酶基因，由于缺失而失去了其部分3'-非翻译区，但仍然具有活性。该突变基因在主要野生型多聚腺苷酸化位点上游19 bp处终止。缺失也去除了该位点之前的AATAAT信号。突变的章鱼碱合酶基因至少包含四个不同的多聚（A）位点。其中最突出的位点与野生型基因的次要多聚（A）位点相同，并且在其之前有一个AATGAATATA序列。其他三个位点位于相邻的植物DNA内，产生杂交的T-DNA/植物DNA转录本。两个最远端的位点可能依赖于一个AATAAATAAA基序，该基序位于距离T-DNA/植物DNA连接处29 bp处。
