The genomic context and co-recruitment of SP1 affect ERRα co-activation by PGC-1α in muscle cells [array]

The peroxisome proliferator-activated receptor γ co-activator 1α (PGC-1α) coordinates the transcriptional network response to promote an improved endurance capacity in skeletal muscle, e.g. by co-activating the estrogen-related receptor α (ERRα) in the regulation of oxidative substrate metabolism. Despite a close functional relationship, the interaction between these two proteins has not been studied on a genomic level. We now mapped the genome-wide binding of ERRα to DNA in skeletal muscle cell line with elevated PGC-1α and linked the DNA recruitment to global PGC-1α target gene regulation. We found that, surprisingly, ERRα co-activation by PGC-1α is only observed in the minority of all PGC-1α recruitment sites. Nevertheless, a majority of PGC-1α target gene expression is dependent on ERRα. Intriguingly, the interaction between these two proteins is controlled by the genomic context of response elements, in particular the relative GC and CpG content, monomeric and dimeric repeat binding site configuration for ERRα, and adjacent recruitment of the transcription factor SP1. These findings thus not only reveal an unprecedented insight into the regulatory network underlying muscle cell plasticity, but also strongly link the genomic context of DNA response elements to control transcription factor - co-regulator interactions. We used microarrays to detect changes in gene expression in C2C12 cells following PGC-1alpha over-expression or GFP (control) over-expression. We used 3 biological replicates for each condition. The samples were: shGFP with GFP viral infection, shGFP with PGC-1alpha viral infection, shERRa with PGC-1alpha viral infection and the ERRa inverse agonist XCT790.

过氧化物酶体增殖物激活受体γ辅激活因子1α（peroxisome proliferator-activated receptor γ co-activator 1α，PGC-1α）可协同调控转录网络应答，以增强骨骼肌的耐力表型，例如通过共激活雌激素相关受体α（estrogen-related receptor α，ERRα）参与氧化底物代谢的调控。尽管二者功能关联密切，但目前尚未在基因组层面解析这两种蛋白的相互作用机制。本研究在过表达PGC-1α的骨骼肌细胞系中，绘制了ERRα与DNA结合的全基因组结合图谱，并将DNA招募事件与PGC-1α全局靶基因的调控过程相关联。令人意外的是，PGC-1α对ERRα的共激活作用仅发生于少数PGC-1α结合位点中；尽管如此，绝大多数PGC-1α靶基因的表达仍依赖于ERRα。有趣的是，二者的相互作用受应答元件的基因组背景调控，具体包括GC与CpG的相对含量、ERRα的单体及二聚体重复结合位点构型，以及转录因子SP1的邻近招募。本研究不仅首次揭示了调控骨骼肌细胞可塑性的潜在调控网络，还明确建立了DNA应答元件的基因组背景与转录因子-辅激活因子相互作用调控之间的关联。本研究采用基因芯片技术，检测了C2C12细胞在过表达PGC-1α或GFP（对照）后的基因表达变化。每组实验均设置3次生物学重复，所使用的样本包括：GFP病毒感染的shGFP细胞、PGC-1α病毒感染的shGFP细胞、PGC-1α病毒感染的shERRα细胞，以及添加ERRα反向激动剂XCT790的样本。