Wu L, Ueda T, Messing J
Waksman Institute, Rutgers, State University of New Jersey, Piscataway 08855.
Plant J. 1993 Sep;4(3):535-44. doi: 10.1046/j.1365-313x.1993.04030535.x.
Cis-regulatory elements involved in the mRNA 3'-end processing of the 27 kDa zein gene have been investigated by deletion and site-directed mutagenesis analyses. In the 3' flanking region of the 27 kDa zein gene, several AATAAA-like sequences and a sequence resembling the mammalian GT-rich sequence are present around the polyadenylation sites. Among the multiple AATAAA-like sequences, the duplicated AATGAA motifs, located 30-40 bp upstream from the polyadenylation sites, have been shown to play roles as polyadenylation signals. Although either of the two AATGAA motifs can function as a polyadenylation signal in chimeric gene constructs, the one proximal to the polyadenylation sites is likely to be the functional polyadenylation signal in the 27 kDa zein gene. Deletion of the downstream GT-rich sequence as well as alteration of the sequence surrounding the poly-adenylation sites has little effect on the mRNA 3'-end processing. However, the sequence elements located upstream from the polyadenylation signals are essential for the mRNA 3'-end processing. Mutations in the AATGAA motifs or the upstream sequences reduced the level of a reporter gene expression. A model depicting the mechanism involved in the 3'-end processing of the 27 kDa zein mRNA is presented.
通过缺失和定点诱变分析，对参与27kDa玉米醇溶蛋白基因mRNA 3'末端加工的顺式作用元件进行了研究。在27kDa玉米醇溶蛋白基因的3'侧翼区域，多聚腺苷酸化位点周围存在几个AATAAA样序列和一个类似于哺乳动物富含GT序列的序列。在多个AATAAA样序列中，位于多聚腺苷酸化位点上游30 - 40bp处的重复AATGAA基序已被证明作为多聚腺苷酸化信号发挥作用。虽然两个AATGAA基序中的任何一个在嵌合基因构建体中都可以作为多聚腺苷酸化信号发挥作用，但靠近多聚腺苷酸化位点的那个基序可能是27kDa玉米醇溶蛋白基因中的功能性多聚腺苷酸化信号。下游富含GT序列的缺失以及多聚腺苷酸化位点周围序列的改变对mRNA 3'末端加工影响很小。然而，位于多聚腺苷酸化信号上游的序列元件对于mRNA 3'末端加工是必不可少的。AATGAA基序或上游序列中的突变降低了报告基因的表达水平。本文提出了一个描述27kDa玉米醇溶蛋白mRNA 3'末端加工机制的模型。
