Context specific regulation of microRNA targets in the immune system (P1142)

Abstract

Abstract MicroRNAs (miRNAs) are key gene expression regulators—their misexpression can cause both immune dysfunction and cancer. However, most miRNA targets remain unknown, limiting mechanistic insight. Combining genetic and biochemical approaches we generated a transcriptome-wide map of miR-155 targets in T cells. High throughput sequencing of cross-linked immunoprecipitated (HITS-CLIP) Argonaute bound transcript fragments in miR-155 sufficient and deficient cells identified hundreds of direct targets for this miRNA in T cells. This map shed insight on known and novel miRNA phenotypes and demonstrated that miRNAs directly regulate transcripts without canonical target motifs. In addition to T cells, miR-155 is expressed in many innate and adaptive immune cells following activation and its deletion leads to varied cell-type specific phenotypes. We hypothesized that miRNAs have diverse functions in different contexts through regulation of different targets. To reveal the extent and mechanism of context specific miRNA targeting, we employed RNA-seq and HITS-CLIP in wild type and miR-155 deficient T cells, B cells, and dendritic cells. Furthermore, we employed polyA-seq to determine how alternative polyadenylation affects context specific targeting. Immune system complexity is generated from a limited set of genes; by revealing how regulatory factors are repurposed in different cell types, our studies will provide insight into fundamental mechanisms of immunological gene regulation.