微RNA（MicroRNAs）是1993年在線蟲(chóng)中發(fā)現(xiàn)的抑制性小RNA分子，廣泛分布在復(fù)雜動(dòng)物中,。人們普遍假設(shè),，它們是當(dāng)動(dòng)物形成雙側(cè)對(duì)稱(chēng)性（即動(dòng)物身體結(jié)構(gòu)復(fù)雜到有前部和后部以及上部和下部）時(shí)作為微調(diào)基因表達(dá)的一種方式而出現(xiàn)的。
新的研究工作（這項(xiàng)工作是基于對(duì)三種“基底后生動(dòng)物門(mén)”的代表動(dòng)物（一種扁盤(pán)動(dòng)物,、一種海綿和一種?？┘耙环N單細(xì)胞“領(lǐng)鞭毛蟲(chóng)”的總RNA內(nèi)容所做測(cè)序進(jìn)行的）表明，微RNA出現(xiàn)的時(shí)間要比人們以前所想的長(zhǎng)得多,。調(diào)控性微RNA通道似乎是在后生動(dòng)物演化過(guò)程中非常早的時(shí)候出現(xiàn)的——是當(dāng)多細(xì)胞生命方式出現(xiàn)時(shí)出現(xiàn)的,，盡管這種機(jī)制后來(lái)在一些生命分支中丟失了。（生物谷Bioon.com）
生物谷推薦原始出處：
Nature 455, 1193-1197 (30 October 2008) | doi:10.1038/nature07415
Early origins and evolution of microRNAs and Piwi-interacting RNAs in animals
Andrew Grimson1,2, Mansi Srivastava4, Bryony Fahey3, Ben J. Woodcroft3, H. Rosaria Chiang1,2, Nicole King4, Bernard M. Degnan3, Daniel S. Rokhsar4,5 & David P. Bartel1,2
1 Whitehead Institute for Biomedical Research, 9 Cambridge Center, Cambridge, Massachusetts 02142, USA
2 Howard Hughes Medical Institute, Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
3 School of Integrative Biology, University of Queensland, Brisbane 4072, Australia
4 Department of Molecular and Cell Biology and Center for Integrative Genomics, University of California at Berkeley, Berkeley, California 94720, USA
5 Department of Energy, Joint Genome Institute, Walnut Creek, California 94598, USA
In bilaterian animals, such as humans, flies and worms, hundreds of microRNAs (miRNAs), some conserved throughout bilaterian evolution, collectively regulate a substantial fraction of the transcriptome. In addition to miRNAs, other bilaterian small RNAs, known as Piwi-interacting RNAs (piRNAs), protect the genome from transposons. Here we identify small RNAs from animal phyla that diverged before the emergence of the Bilateria. The cnidarian Nematostella vectensis (starlet sea anemone), a close relative to the Bilateria, possesses an extensive repertoire of miRNA genes, two classes of piRNAs and a complement of proteins specific to small-RNA biology comparable to that of humans. The poriferan Amphimedon queenslandica (sponge), one of the simplest animals and a distant relative of the Bilateria, also possesses miRNAs, both classes of piRNAs and a full complement of the small-RNA machinery. Animal miRNA evolution seems to have been relatively dynamic, with precursor sizes and mature miRNA sequences differing greatly between poriferans, cnidarians and bilaterians. Nonetheless, miRNAs and piRNAs have been available as classes of riboregulators to shape gene expression throughout the evolution and radiation of animal phyla.
