当基因转录成RNA时，聚合酶延伸到超过蛋白编码的部分，来形成“3?未翻译区域” (UTR)，该区域含调控性序列并帮助翻译。腺嘌呤长束被添加到3? UTR，转录组测序的标准方法基于 “poly(A)”尾巴的杂合。Jan等人报告了转录组测序的一种新的高吞吐量方法，该方法能够避免“poly(A)”方法的局限性，同时他们还利用该新方法为蛔虫中的3? UTR提供了一个更准确的分析结果。（生物谷Bioon.com）
生物谷推荐原文出处：
Nature doi:10.1038/nature09616
Formation, regulation and evolution of Caenorhabditis elegans 3′UTRs
Calvin H. Jan,Robin C. Friedman,J. Graham Ruby& David P. Bartel
Post-transcriptional gene regulation frequently occurs through elements in mRNA 3′ untranslated regions (UTRs)1, 2. Although crucial roles for 3′UTR-mediated gene regulation have been found in Caenorhabditis elegans3, 4, 5, most C. elegans genes have lacked annotated 3′UTRs6, 7. Here we describe a high-throughput method for reliable identification of polyadenylated RNA termini, and we apply this method, called poly(A)-position profiling by sequencing (3P-Seq), to determine C. elegans 3′UTRs. Compared to standard methods also recently applied to C. elegans UTRs8, 3P-Seq identified 8,580 additional UTRs while excluding thousands of shorter UTR isoforms that do not seem to be authentic. Analysis of this expanded and corrected data set suggested that the high A/U content of C. elegans 3′UTRs facilitated genome compaction, because the elements specifying cleavage and polyadenylation, which are A/U rich, can more readily emerge in A/U-rich regions. Indeed, 30% of the protein-coding genes have mRNAs with alternative, partially overlapping end regions that generate another 10,480 cleavage and polyadenylation sites that had gone largely unnoticed and represent potential evolutionary intermediates of progressive UTR shortening. Moreover, a third of the convergently transcribed genes use palindromic arrangements of bidirectional elements to specify UTRs with convergent overlap, which also contributes to genome compaction by eliminating regions between genes. Although nematode 3′UTRs have median length only one-sixth that of mammalian 3′UTRs, they have twice the density of conserved microRNA sites, in part because additional types of seed-complementary sites are preferentially conserved. These findings reveal the influence of cleavage and polyadenylation on the evolution of genome architecture and provide resources for studying post-transcriptional gene regulation.