Hypoxia-induced phase separation of ZHX2 drives 3D chromatin remodeling and cancer metastasis

Hypoxia and dysregulation of three-dimensional (3D) chromatin architecture can bothactivate oncogenic transcriptomic profiles, thus contributing to tumor malignancy. Buthow hypoxia regulates 3D chromatin architecture remains unknown. Here, we find thatthe transcription factor, zinc fingers and homeoboxes 2 (ZHX2), generates liquid-liquidphase separation (LLPS) under hypoxia, thus promoting its occupancy on chromatinand activating transcription for a cluster of oncogenes, that is enriched by metastaticgenes distinct from targets of hypoxia-inducible factor (HIF) and pathologically relevantto breast cancer. Mechanistically, hypoxia induces the LLPS of ZHX2 via a proline-richintrinsically disordered region (IDR) in the nuclear localization sequence (NLS), therebyenhancing the phosphorylation of ZHX2 at S625 and S628 that incorporates CCCTCbindingfactor (CTCF) in condensates to reorganize chromatin looping, consequentlyresulting in oncogenic super-enhancer formation and breast cancer metastasis. Thisfundamental mechanism provides significant insight into oncogene activation andsuggests a phase separation-based therapeutic strategy for cancer.