RNA-bound PGC-1α controls gene expression in liquid-like nuclear condensates
The peroxisome-proliferator-activated receptor-{gamma} coactivator-1 (PGC-1) integrates environmental cues by controlling complex transcriptional networks in various metabolically active tissues. However, it is unclear how a transcriptional coregulator coordinates dynamic biological programs in response to multifaceted stimuli such as endurance training or fasting. Here, we discovered a central function of the poorly understood C-terminal domain (CTD) of PGC-1 to bind RNAs and assemble multi-protein complexes. Surprisingly, in addition to controlling the coupling of transcription and processing of target genes, RNA binding is indispensable for the recruitment of PGC-1 to chromatin into liquid-like nuclear condensates, which compartmentalize and regulate active transcription. These results demonstrate a hitherto unsuspected molecular mechanism by which complexity in the regulation of large transcriptional networks by PGC-1 is achieved. These findings are not only essential for the basic understanding of transcriptional coregulator-driven control of biological programs, but will also help to devise new strategies to modulate these processes in pathological contexts in which PGC-1 function is dysregulated, such as type 2 diabetes, cardiovascular diseases or skeletal muscle wasting.