Nanog maintains pluripotency of mouse embryonic stem cells by inhibiting NFκB and cooperating with Stat3

Embryonic stem (ES) cells are pluripotent cells derived from the inner cell mass of blastocysts. Self-renewal of mouse ES cells depends on activation of Stat3 by leukaemia inhibitory factor (LIF) in collaboration with bone morphogenetic protein signalling(1-3). The transcription factor Nanog is essential in maintaining pluripotency(4,5) but the mechanisms involved are poorly understood. Here we examine the functional interactions of Nanog with the Stat3 and NF kappa B pathways. Nanog and Stat3 were found to bind to and synergistically activate Stat3-dependent promoters. We also found that Nanog binds to NF kappa B proteins; however, Nanog binding inhibited transcriptional activity of NF kappa B proteins. Endogenous NF kappa B activity and target-gene expression increased during differentiation of ES cells. Overexpression of NF kappa B proteins promoted differentiation, whereas inhibition of NF kappa B signalling, either by genetic ablation of the Ikbkg gene or overexpression of the I kappa B alpha super-repressor, increased expression of pluripotency markers. We conclude that Nanog represses the pro-differentiation activities of NF kappa B and cooperates with Stat3 to maintain pluripotency.