Epigenetic regulation of macrophage cholesterol efflux and atherogenesis by a long noncoding RNA

Nuclear receptors are important conduits between environmental cues and gene expression, but the molecular events governing spatial variation in their responses remain poorly understood. Here we outline an important role for a non-coding RNA in modulating the cell type-specific actions of the cholesterol-activated nuclear receptor LXR. LXR regulates the expression of genes involved in responses to excess cholesterol and has been causally linked to the pathogenesis and treatment of prevention and atherosclerosis in animals. We identify the lncRNA MeXis as an amplifier of LXR-dependent transcription of the critical cholesterol efflux gene Abca1. MeXis interacts with and guides the promoter binding of the nuclear receptor transcriptional coactivator DDX17. Loss of MeXis in murine immune cells has a marked impact on chromosome architecture at the Abca1 locus, impairs cellular responses to cholesterol overload, and accelerates the development of atherosclerosis. Our findings define MeXis as a lncRNA gatekeeper that modifies the actions of LXR in lipid-dependent control of macrophage gene expression. This has important implications for mechanisms that underlie spatial activation patterns of nuclear receptors. Our work opens a new gateway to targeting reverse cholesterol transport since it is conceivable that therapeutic approaches that enhance MeXis activity might reduce foam cell formation and atherogenesis. Peritoneal macrophages were isolated from either WT or KO animals and treated for 3 hours with or without GW using DMSO as control. Using four replicates per condition libraries were prepared using the Nextera Tn5 Transposase kit (Illumina) as described by Buenrostro and colleagues with slight modifications