Background: The exit from pluripotency or pluripotent-somatic transition (PST) landmarks an event of early mammalian embryonic development, representing a model for cell fate transition.

Results: In this study, using a robust JUN-induced PST within 8 h as a model, we investigate the chromatin accessibility dynamics (CAD) as well as the behaviors of corresponding chromatin remodeling complex SS18/BAFs, to probe the key events at the early stage of PST. Here, we report that, JUN triggers the open of 34661 chromatin sites within 4 h, accomplished with the activation of somatic genes, such as Anxa1, Fosl1. ChIP-seq data reveal a rapid relocation of SS18/BAFs from pluripotent loci to AP-1 associated ones. Consistently, the knockdown of Brg1, core component of BAF complexes, leads to failure in chromatin opening but not closing, resulting in delay for JUN induced PST. Notably, the direct interaction between SS18/BAFs and JUN-centric protein complexes is undetectable by IP-MS. Instead, we show that H3K27ac deposited by cJUN dependent process regulates SS18/BAFs complex to AP1-containing loci and facilitate chromatin opening and gene activation.