title: Testing hypotheses on the rate of molecular evolution in relation to gene expression using microRNAs.
abstract: There exists an inverse relationship between the rate of molecular evolution and the level of gene expression. Among the many explanations, the "toxic-error" hypothesis is a most general one, which posits that processing errors may often be toxic to the cells. However, toxic errors that constrain the evolution of highly expressed genes are often difficult to measure. In this study, we test the toxic-error hypothesis by using microRNA (miRNA) genes because their processing errors can be directly measured by deep sequencing. A miRNA gene consists of a small mature product (≈22 nt long) and a "backbone." Our analysis shows that (i) like the mature miRNA, the backbone is highly conserved; (ii) the rate of sequence evolution in the backbone is negatively correlated with expression; and (iii) although conserved between distantly related species, the error rate in miRNA processing is also negatively correlated with the expression level. The observations suggest that, as a miRNA gene becomes more highly (or more ubiquitously) expressed, its sequence evolves toward a structure that minimizes processing errors.
authors.affiliation: State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-sen (Zhongshan) University, Guangzhou 510275, China.
authors.forename: Yang
authors.initials: Y
authors.lastname: Shen
authors.forename: Yang
authors.initials: Y
authors.lastname: Lv
authors.forename: Lei
authors.initials: L
authors.lastname: Huang
authors.forename: Wensheng
authors.initials: W
authors.lastname: Liu
authors.forename: Ming
authors.initials: M
authors.lastname: Wen
authors.forename: Tian
authors.initials: T
authors.lastname: Tang
authors.forename: Rui
authors.initials: R
authors.lastname: Zhang
authors.forename: Eric
authors.initials: E
authors.lastname: Hungate
authors.forename: Suhua
authors.initials: S
authors.lastname: Shi
authors.forename: Chung-I
authors.initials: CI
authors.lastname: Wu
mesh_terms: D000465:Algorithms; D000818:Animals; D001483:Base Sequence; D003198:Computer Simulation; D004330:Drosophila / Q000145:classification / Q000235:genetics; D004331:Drosophila melanogaster / Q000235:genetics; D019143:Evolution, Molecular; D015870:Gene Expression / Q000235:genetics*; D014644:Genetic Variation; D035683:MicroRNAs / Q000235:genetics*; D008957:Models, Genetic; D012689:Sequence Homology, Nucleic Acid; D013045:Species Specificity
chemical_list: D035683:MicroRNAs