Myc and SAGA Rewire an Alternative Splicing Network During Early Somatic Cell Reprogramming [Reprogramming_ChIPSEQ]

Embryonic stem cells are maintained in a self-renewing and pluripotent state by multiple regulatory pathways. Pluripotent-specific transcriptional networks are sequentially reactivated as somatic cells reprogram to achieve pluripotency. How epigenetic regulators modulate this process and contribute to somatic cell reprogramming is not clear. Here we perform a functional RNAi screen to identify the earliest epigenetic regulators required for reprogramming. We identify components of the SAGA histone acetyltransferase complex, in particular Gcn5, as critical regulators of reprogramming initiation. Furthermore, we show in mouse pluripotent stem cells that Gcn5 strongly associates with Myc and that upon initiation of somatic reprogramming, Gcn5 and Myc form a positive feed forward loop that activates a distinct alternative splicing network and the early acquisition of pluripotency-associated splicing events. These studies expose a Myc-SAGA pathway that drives expression of an essential alternative splicing regulatory network during somatic cell reprogramming. Examination of Myc-chromatin interactions in reprogramming cells胚胎干细胞 (embryonic stem cells) 通过多条调控通路维持自我更新与多能性状态。体细胞重编程以获得多能性的过程中，多能性特异性转录调控网络会被依次重新激活。目前表观遗传调控因子如何调控这一过程，并促进体细胞重编程，尚不清楚。本研究通过功能RNA干扰 (RNAi) 筛选，鉴定出了重编程起始阶段所需的早期关键调控因子。我们发现SAGA组蛋白乙酰转移酶复合物 (SAGA histone acetyltransferase complex) 的组分，尤其是Gcn5，是重编程起始的关键调控因子。此外，我们在小鼠多能干细胞中证实，Gcn5可与Myc紧密结合；在体细胞重编程启动后，Gcn5与Myc形成正向反馈环路，激活独特的可变剪接调控网络，并早期诱导多能性相关剪接事件的发生。本研究揭示了一条Myc-SAGA通路，该通路可在体细胞重编程过程中驱动必需的可变剪接调控网络的表达。我们对重编程细胞中的Myc-染色质相互作用进行了分析。