MYC drives left-handed Z-DNA formation to shape gene expression.

DNA topology is critical for regulating transcription and maintaining cellular homeostasis. Z-DNA is a left-handed DNA helix in regions with high transcriptional activity. Its physiological function remains poorly understood. Here, we demonstrate that oncoprotein MYC induces the formation of Z-DNA by recruiting the chromatin remodeler FACT, independent of RNA Polymerase II activity. FACT facilitates Z-DNA formation by remodeling H2A/H2B dimers within intact nucleosomes. Additionally, the phosphorylation of FACT regulates its liquid-liquid phase separation, promoting its efficient recruitment to chromatin by MYC. Through a genome-wide analysis and characterization of engineered Z-DNA promoters, we found that Z-DNA directly facilitates the loading of RNA Polymerase II, thereby promoting transcriptional activity. This study elucidates the molecular mechanisms of Z-DNA dynamics and emphasizes its functional importance in transcriptional regulation, providing insights into the role of left-handed DNA structures in chromatin biology and MYC-driven cancer.