Hiding in Plain Sight

Small peptides encoded by a so-called long noncoding RNA play an active role in regulating gene expression. The roles of RNA in protein synthesis are well known—as a template for translation of cellular proteins and as ribosomal and transfer RNA (tRNA). However, more recent studies have elucidated the intricate functions of other abundant types of RNAs, such as micro RNAs (miRNAs) and small inhibitory RNAs (siRNAs), which control the expression of target messenger RNAs (mRNAs) (1). Despite this extensive catalog of functional RNAs, many transcribed RNAs still lack an obvious protein product or the characteristic structure of known functional RNAs. Except for a few examples involved in gene silencing and imprinting (2, 3), the importance of so-called long noncoding RNAs (lncRNA) remains controversial (4, 5). On page 336 of this issue, Kondo et al. (6) show that an RNA called polished-rice (pri) has features of a lncRNA, but encodes tiny peptides that control gene expression during development in the fruit fly Drosophila melanogaster.

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