专题：Nature系列
利用单分子高通量测序方法对来自人类细胞的短RNA（少于200个核苷酸）所做的一项分析，发现了一类有所不同的、以前未知的短RNA。
它们在其5'端都有相同的“尾巴”，由非基因组编码的“polyU”残体的一个序列组成。这一点，再加上关于这些RNA与由已知RNA构成的3'端密切相关的发现，指出了在人类细胞中存在一个新型RNA复制机制。
生物谷推荐原文出处：
Nature doi:10.1038/nature09190
New class of gene-termini-associated human RNAs suggests a novel RNA copying mechanism
Philipp Kapranov,Fatih Ozsolak,Sang Woo Kim,Sylvain Foissac,Doron Lipson,Chris Hart,Steve Roels,Christelle Borel,Stylianos E. Antonarakis,A. Paula Monaghan,Bino John" Patrice M. Milos
Small (&200 nucleotide) RNA (sRNA) profiling of human cells using various technologies demonstrates unexpected complexity of sRNAs with hundreds of thousands of sRNA species present1, 2, 3, 4. Genetic and in vitro studies show that these RNAs are not merely degradation products of longer transcripts but could indeed have a function1, 2, 5. Furthermore, profiling of RNAs, including the sRNAs, can reveal not only novel transcripts, but also make clear predictions about the existence and properties of novel biochemical pathways operating in a cell. For example, sRNA profiling in human cells indicated the existence of an unknown capping mechanism operating on cleaved RNA2, a biochemical component of which was later identified6. Here we show that human cells contain a novel type of sRNA that has non-genomically encoded 5′ poly(U) tails. The presence of these RNAs at the termini of genes, specifically at the very 3′ ends of known mRNAs, strongly argues for the presence of a yet uncharacterized endogenous biochemical pathway in cells that can copy RNA. We show that this pathway can operate on multiple genes, with specific enrichment towards transcript-encoding components of the translational machinery. Finally, we show that genes are also flanked by sense, 3′ polyadenylated sRNAs that are likely to be capped.
