The Role of microRNAs in Bovine Infection and Immunity

Despite their widespread roles as regulators of gene expression, important questions remain about target regulation by microRNAs. Animal microRNAs were originally thought to repress target translation, with little or no influence on mRNA abundance, whereas the reverse was thought to be true in plants. Now, however, it is clear that microRNAs can induce mRNA degradation in animals and, conversely, translational repression in plants. Recent studies have made important advances in elucidating the relative contributions of these two different modes of target regulation by microRNAs. They have also shed light on the specific mechanisms of target silencing, which, although it differs fundamentally between plants and animals, shares some common features between the two kingdoms.

Mammalian microRNAs (miRNAs) have recently been identified as important regulators of gene expression, and they function by repressing specific target genes at the post-transcriptional level. Now, studies of miRNAs are resolving some unsolved issues in immunology. Recent studies have shown that miRNAs have unique expression profiles in cells of the innate and adaptive immune systems and have pivotal roles in the regulation of both cell development and function. Furthermore, when miRNAs are aberrantly expressed they can contribute to pathological conditions involving the immune system, such as cancer and autoimmunity; they have also been shown to be useful as diagnostic and prognostic indicators of disease type and severity. This Review discusses recent advances in our understanding of both the intended functions of miRNAs in managing immune cell biology and their pathological roles when their expression is dysregulated.

MicroRNAs (miRNAs) control gene expression in animals, plants, and unicellular eukaryotes by promoting degradation or repressing translation of target mRNAs. miRNA expression is often tissue specific and developmentally regulated, and regulation occurs both transcriptionally and posttranscriptionally. This regulation is crucial, as alteration of miRNA expression has been linked to human diseases, including several cancers. Here, we discuss recent studies that shed light on how multiple steps in the miRNA biogenesis pathway are regulated to modulate miRNA function in animals. Copyright (c) 2010 Elsevier Inc. All rights reserved.