Target RNA–Directed Trimming and Tailing of Small Silencing RNAs

• DOI: 10.1126/science.1187058
• Publication Date: 2010-06-17T18:10:11Z
• Authors: Stefan L. Ameres; Michael D. Horwich; Jui-Hung Hung; Jia Xu; Megha Ghildiyal; Zhiping Weng; Phillip D. Zamore
• Keywords: RNA Caps; 0301 basic medicine; RNA Stability; Messenger; Green Fluorescent Proteins; 612; Small Interfering; Methylation; Models, Biological; Cell Line; RNA, Complementary; Molecular Genetics; 03 medical and health sciences; Models; Complementary; Nucleic Acids; Animals; Drosophila Proteins; Humans; RNA-Induced Silencing Complex; RNA, Messenger; Eukaryotic Initiation Factors; RNA, Small Interfering; Molecular Biology; Base Pairing; 2. Zero hunger; Nucleotides; Computational Biology; Methyltransferases; Biological; and Nucleosides; *Base Pairing; MicroRNAs; Drosophila melanogaster; Argonaute Proteins; RNA; *RNA Stability

Close, But Not Too Close

MicroRNAs (miRNAs) in plants are generally highly complementary to their target RNAs, yet, in most animal miRNAs, only the ∼8-nucleotide “seeds” sequence bases pair fully with the target, with few base pairs between the remainder of the miRNA and target. Plant miRNAs are methylated at their 3′ ends, whereas animals' miRNAs are not.

Ameres et al.

(p. 1534 ; see the Perspective by

Pasquinelli

) noticed that, in fruit flies, miRNAs engineered to have high complementarity to target RNAs were present at reduced levels. These miRNAs were trimmed and uridylated at their 3′ ends, features involved in RNA degradation. Fly small interfering RNAs, all of which are methylated at their 3′ ends, were unaffected, unless the methylating enzyme, Hen1, was mutated. Thus, 3′-methylation may prevent complementarity-driven remodeling and degradation of small RNAs.