Genome-wide Mapping of RELA(p65) Binding Identifies E2F1 as a Transcriptional Activator Recruited by NF-κB upon TLR4 Activation

NF-κB is a key mediator of inflammation. Here, we mapped the genome-wide loci bound by the RELA subunit of NF-κB in lipopolysaccharide (LPS)-stimulated human monocytic cells, and together with global gene expression profiling, found an overrepresentation of the E2F1-binding motif among RELA-bound loci associated with NF-κB target genes. Knockdown of endogenous E2F1 impaired the LPS inducibility of the proinflammatory cytokines CCL3(MIP-1α), IL23A(p19), TNF-α, and IL1-β. Upon LPS stimulation, E2F1 is rapidly recruited to the promoters of these genes along with p50/RELA heterodimer via a mechanism that is dependent on NF-κB activation. Together with the observation that E2F1 physically interacts with p50/RELA in LPS-stimulated cells, our findings suggest that NF-κB recruits E2F1 to fully activate the transcription of NF-κB target genes. Global gene expression profiling subsequently revealed a spectrum of NF-κB target genes that are positively regulated by E2F1, further demonstrating the critical role of E2F1 in the Toll-like receptor 4 pathway.