Batt D B, Luo Y, Carmichael G G
Department of Microbiology, University of Connecticut Health Center, Farmington 06030.
Nucleic Acids Res. 1994 Jul 25;22(14):2811-6. doi: 10.1093/nar/22.14.2811.
The processes of pre-mRNA 3'-end cleavage and polyadenylation have been closely linked to transcription termination by RNA polymerase II. We have studied the relationship between polyadenylation and transcription termination in gene constructs containing tandem poly(A) signals, at least one of which is the inefficient polyomavirus late poly(A) site. When identical tandem viral signals were separated by fewer than 400 bp, they competed for polyadenylation. The upstream site was always chosen preferentially, but relative site choice was influenced by the distance between the signals. All of these constructs showed the same low level of transcription termination as wild type polyomavirus, which contains a single late poly(A) site. When tandem poly(A) signals were not identical, a stronger downstream signal could outcompete a weaker upstream signal for polyadenylation without altering the efficiency of transcription termination characteristic for use of the upstream signal. Thus, if a weak polyoma virus late poly(A) signal (associated with inefficient transcription termination) preceded a strong rabbit beta-globin signal (associated with efficient transcription termination), termination remained inefficient, but the distal signal was most often chosen for polyadenylation. These results are consistent with independent regulation of polyadenylation and transcription termination in this system and are discussed in light of current models for the dependence of transcription termination on a functional poly(A) site.
前体信使核糖核酸（pre-mRNA）3'端切割和聚腺苷酸化过程与RNA聚合酶II的转录终止密切相关。我们研究了在含有串联聚腺苷酸（poly(A)）信号的基因构建体中聚腺苷酸化与转录终止之间的关系，其中至少有一个是效率低下的多瘤病毒晚期聚(A)位点。当相同的串联病毒信号被少于400个碱基对分隔时，它们会竞争聚腺苷酸化。上游位点总是被优先选择，但相对位点选择受信号之间距离的影响。所有这些构建体都表现出与野生型多瘤病毒相同的低水平转录终止，野生型多瘤病毒含有单个晚期聚(A)位点。当串联聚(A)信号不同时，较强的下游信号在聚腺苷酸化方面可以胜过较弱的上游信号，而不会改变使用上游信号时的转录终止效率。因此，如果一个弱的多瘤病毒晚期聚(A)信号（与低效转录终止相关）位于一个强的兔β-珠蛋白信号（与高效转录终止相关）之前，终止仍然低效，但远端信号最常被选择用于聚腺苷酸化。这些结果与该系统中聚腺苷酸化和转录终止的独立调节一致，并根据当前转录终止依赖于功能性聚(A)位点的模型进行了讨论。
