Maintenance of stem-cell identity requires proper regulation of enhancer 
activity. Both transcription factors OCT4/SOX2/NANOG and histone 
methyltransferase complexes MLL/SET1 were shown to regulate enhancer activity, 
but how they are regulated in embryonic stem cells (ESCs) remains further 
studies. Here, we report a transcription factor BACH1, which directly interacts 
with OCT4/SOX2/NANOG (OSN) and MLL/SET1 methyltransferase complexes and 
maintains pluripotency in mouse ESCs (mESCs). BTB domain and bZIP domain of 
BACH1 are required for these interactions and pluripotency maintenance. Loss of 
BACH1 reduced the interaction between NANOG and MLL1/SET1 complexes, and 
decreased their occupancy on chromatin, and further decreased H3 lysine 4 
trimethylation (H3K4me3) level on gene promoters and (super-) enhancers, leading 
to decreased enhancer activity and transcription activity, especially on 
stemness-related genes. Moreover, BACH1 recruited NANOG through chromatin 
looping and regulated remote NANOG binding, fine-tuning enhancer-promoter 
activity and gene expression. Collectively, these observations suggest that 
BACH1 maintains pluripotency in ESCs by recruiting NANOG and MLL/SET1 complexes 
to chromatin and maintaining the trimethylated state of H3K4 and 
enhancer-promoter activity, especially on stemness-related genes.