Sheets M D, Ogg S C, Wickens M P
Cell and Molecular Biology Program, College of Agriculture and Life Sciences, University of Wisconsin, Madison 53706.
Nucleic Acids Res. 1990 Oct 11;18(19):5799-805. doi: 10.1093/nar/18.19.5799.
Three sequences in the vicinity of poly (A) addition sites are conserved among vertebrate mRNAs. We analyze the effects of single base changes in each position of AAUAAA and in the nucleotide to which poly (A) is added on 3' end formation in vitro. All 18 possible single base changes of the AAUAAA sequence greatly reduce addition of poly (A) to RNAs that end at the poly (A) addition site, and prevent cleavage of RNAs that extend beyond. The magnitude of reduction varies greatly with the position changed and the base introduced. For any given mutation, cleavage and polyadenylation are reduced to similar extents, strongly suggesting that the same factor interacts with AAUAAA in both reactions. Mutations at and near the conserved adenosine to which poly (A) is added disturb the accuracy, but not the efficiency, of 3' end formation. For example, point mutations at the conserved adenosine shift the 3' end of the most abundant 5' half-molecule downstream by a single nucleotide. The mechanism by which these mutations might exert their effects on the precision of 3' end formation are discussed.
聚腺苷酸化位点附近的三个序列在脊椎动物mRNA中是保守的。我们分析了AAUAAA每个位置的单碱基变化以及添加聚腺苷酸的核苷酸对体外3'端形成的影响。AAUAAA序列的所有18种可能的单碱基变化都大大减少了聚腺苷酸添加到在聚腺苷酸化位点处终止的RNA上，并阻止了延伸超过该位点的RNA的切割。减少的程度因变化的位置和引入的碱基而异。对于任何给定的突变，切割和聚腺苷酸化减少到相似的程度，强烈表明相同的因子在这两个反应中与AAUAAA相互作用。在添加聚腺苷酸的保守腺苷处及附近的突变会干扰3'端形成的准确性，但不影响其效率。例如，保守腺苷处的点突变会使最丰富的5'半分子的3'端向下游移动一个核苷酸。本文讨论了这些突变可能对3'端形成精度产生影响的机制。
