PWOs repress gene transcription by regulating chromatin structures in Arabidopsis.

PWWP-DOMAIN INTERACTOR OF POLYCOMBS (PWO) family proteins play a vital role in regulating plant development. However, the molecular mechanisms of how PWOs regulate chromatin structure is elusive. Our data show that the PWO1 binding sites are enriched with positive modifications but exclusive with H3K27me3. Moreover, PWO1 binds to the H3K27me3-enriched compartment domain (H3K27me3-CD) boundary regions, and functions to maintain the boundary strength. Meanwhile, we found that PWOs and Polycomb repressive complex 2 (PRC2) function parallelly in maintaining H3K27me3-CDs' structure. Loss of either PWOs or PRC2 leads to H3K27me3-CD strength reduction, B to A compartment switching as well as the H3K27me3-CD relocating away from the nuclear periphery. Additionally, PWOs and lamin-like proteins collaborate to regulate multiple chromatin structures to repress gene transcription within H3K27me3-CDs. We conclude that PWOs maintain H3K27me3-CDs' repressive state and regulate their spatial position in the nucleus.