Mouse embryonic stem cells cultured with MEK (mitogen-activated protein kinase kinase) and GSK3 (glycogen synthase kinase 3) inhibitors (2i) more closely resemble the inner cell mass of preimplantation blastocysts than those cultured with SL [serum/leukemia inhibitory factor (LIF)]. The transcriptional mechanisms governing this pluripotent ground state are unresolved. Release of promoter-proximal paused RNA polymerase II (Pol2) is a multistep process necessary for pluripotency and cell cycle gene transcription in SL. We show that β-catenin, stabilized by GSK3 inhibition in medium with 2i, supplies transcriptional coregulators at pluripotency loci. This selectively strengthens pluripotency loci and renders them addicted to transcription initiation for productive gene body elongation in detriment to Pol2 pause release. By contrast, cell cycle genes are not bound by β-catenin, and proliferation/self-renewal remains tightly controlled by Pol2 pause release under 2i conditions. Our findings explain how pluripotency is reinforced in the ground state and also provide a general model for transcriptional resilience/adaptation upon network perturbation in other contexts.

用 MEK（丝裂原活化蛋白激酶激酶）和 GSK3（糖原合酶激酶 3）抑制剂 (2i) 培养的小鼠胚胎干细胞比用 SL [血清/白血病抑制因子 (LIF) 培养的胚胎干细胞更接近植入前囊胚的内细胞团。 )]。控制这种多能基态的转录机制尚未解决。启动子近端暂停 RNA 聚合酶 II (Pol2) 的释放是 SL 中多能性和细胞周期基因转录所必需的多步骤过程。我们表明，在具有 2i 的培养基中通过 GSK3 抑制稳定的 β-连环蛋白在多能性基因座提供转录辅助调节剂。这选择性地增强了多能性基因座，并使它们沉迷于转录起始，以进行生产性基因体伸长，从而损害 Pol2 暂停释放。相比之下，细胞周期基因不受β-连环蛋白的约束，增殖/自我更新仍然受到2i条件下Pol2暂停释放的严格控制。我们的研究结果解释了如何在基态增强多能性，并为在其他情况下网络扰动时的转录弹性/适应提供了一个通用模型。