Enhancers that regulateTNFgene transcription in human macrophages in response to TLR3 stimulation

Abstract

AbstractMacrophages play a critical role in inflammatory responses during infections. These cells are activated via stimulation of Toll-like receptors (TLRs) on their cell surface, leading to the production of pro-inflammatory cytokines, including TNF. However, the mechanisms by which enhancers regulateTNFgene transcription in human macrophages, particularly with regards to distal enhancers, remain poorly understood. This study used an unbiased genomic approach to identify six candidate enhancers in human primary alveolar macrophages within a 131 kb region from the transcription start site (TSS) of theTNFgene, covering 13 genes. Of these candidate enhancers, five showed enhancer activity, with three targeting theTNFgene and two targeting neighboring genes. Deletion of the distalTNFE-16 enhancer led to a 73% reduction inTNFgene transcription in response to poly (I:C) stimulation in the THP-1 human leukemia monocytic cell line. Additionally, deletion of the E-7.1/hHS-8 enhancer resulted in a 41% reduction inTNFmRNA, while deletion of the PE enhancer had a lesser effect, resulting in a 52% reduction inTNFgene transcription. Massively parallel reporter assays (MPRA) indicated that the transcription factor AP-1 and EGR2-binding sites at the distalTNFE-16 enhancer were crucial in mediating enhancer activity. This study shows that both distal and proximal enhancers work together to fully transcribe theTNFgene in human macrophages in response to TLR ligand poly (I:C) stimulation.