Polyphosphate as a novel regulator of super-enhancer complexes: disruption of phase separation and gene expression.

Inorganic polyphosphate (polyP) is a highly conserved linear polymer of orthophosphate, present across nearly all living organisms. Its functional diversity, particularly through recently discovered post-translational modifications, has garnered increasing scientific interest. However, its role in gene regulation, especially in mammalian systems, remains unexplored. In this study, we present findings that demonstrate that polyP multi-targets the super-enhancer complex to regulate gene expression, marking a novel mechanism of transcriptional control. We show that polyP modifies key components of the complex, including the Mediator subunit MED1, the coactivator Bromodomain-containing protein 4 (BRD4), and the transcriptional regulator Yin Yang 1 (YY1). This polyP-mediated modification not only disrupts their ability to undergo phase separation but also downregulates the expression of MED1 and BRD4, as well as impairs the nuclear localization of YY1. Furthermore, polyP inhibits YY1 dimer formation and disrupts YY1-mediated DNA looping, leading to suppressed gene expression. These discoveries highlight polyP as a novel regulator of super-enhancer-driven gene transcription and provide new insights into the broader role of polyP in epigenetic regulation. This work uncovers a previously unknown layer of gene control, positioning polyP as a critical player in transcriptional regulation through its interaction with transcription factors and coactivators.