Genome-wide mapping of RELA(p65) binding identifies E2F1 as a transcriptional activator recruited by NF-κB upon TLR4 activation

NF-KB is a key mediator of inflammation. Here, we mapped the genome-wide loci bound by the RELA subunit of NF-kappa B 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-KB target genes. Knockdown of endogenous E2F1 impaired the LPS inducibility of the proinflammatory cytokines CCL3(MIP-1 alpha), IL23A(p19), TNF-alpha, and IL1-beta. 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-KB activation. Together with the observation that E2F1 physically interacts with p50/RELA in LPS-stimulated cells, our findings suggest that NF-KB recruits E2F1 to fully activate the transcription of NF-KB target genes. Global gene expression profiling subsequently revealed a spectrum of NF-kappa B target genes that are positively regulated by E2F1, further demonstrating the critical role of E2F1 in the Toll-like receptor 4 pathway.