The evolution and functional diversification of animal microRNA genes

Abstract

microRNAs (miRNAs) are an abundant class of ~22 nucleotide (nt) regulatory RNAs that are pervasive in higher eukaryotic genomes. In order to fully understand their prominence in genomes, it is necessary to elucidate the molecular mechanisms that can diversify miRNA activities. In this review, we describe some of the many strategies that allow novel miRNA functions to emerge, with particular emphasis on how miRNA genes evolve in animals. These mechanisms include changes in their sequence, processing, or expression pattern; acquisition of miRNA* functionality or antisense processing; and de novo gene birth. The facility and versatility of miRNAs to evolve and change likely underlies how they have become dominant constituents of higher genomes.

Systematic analysis of human microRNA divergence based on evolutionary emergence

“…These results seem to imply that the random hairpin sequences containing more A+U in genome are easier to evolve into new miRNA genes. Liu et al [9] suggested that as antisense regulators, alteration to the sequence of miRNAs will have an impact on their targeting capabilities. So, we investigated base composition at each position in the mature miRNA sequences arising from different evolutionary lineages and the predominant nucleotides at each position are summarized in Fig.…”

“…The phylogenetic distribution and evolution of animal and plant miRNAs have been studied in recent reports [2][3][4][5][6][7][8][9][10][11][12]. In animals, the expansion of miRNAs is an ongoing process [5].…”

Repertoire and evolution of miRNA genes in four divergent nematode species

“…We found that within the Caenorhabditis genus the majority of miRNAs are conserved between species, while P. pacificus miRNAs show a decreased level of conservation. In addition, we show that between species, a change of the dominantly expressed miRNA arm, a process known as arm switching (Liu et al 2008), is a common mechanism. Antisense transcription of miRNA loci (Ruby et al 2007b) is observed for three miRNAs in our data set, and this process could lead to novel miRNAs as well.…”

Is CCDC26 a Novel Cancer-Associated Long-Chain Non-Coding RNA?

“…Among such ncRNAs, microRNAs (miRNAs), small molecule RNAs 18-28 bases long, have been extensively studied over the past decade, and a gene regulatory system called "RNA silencing" has been revealed. In humans, more than 400 miRNAs are known to regulate at least one-third of proteinencoding genes (6)(7)(8)(9)(10). Most miRNAs are generated by processing of long miRNA precursors (pri-miRNAs) (6,9).…”

“…In humans, more than 400 miRNAs are known to regulate at least one-third of proteinencoding genes (6)(7)(8)(9)(10). Most miRNAs are generated by processing of long miRNA precursors (pri-miRNAs) (6,9). Pri-miRNAs are transcribed by RNA polymerase II and 5' cap structures and poly A tails are added, similarly to protein-encoding mRNAs.…”