LAUSR

Significance COP1, an E3 ligase, plays a pivotal role in the regulation of photomorphogenesis in plants. This role is accomplished through its capacity to target and degrade various nuclear substrates via the ubiquitin/26S proteasome system. In this study, we show that COP1 controls global levels of H3K27me3, a histone modification associated with gene repression, through its interaction with a Polycomb protein called VIL1. In the absence of light, COP1 facilitates the degradation of VIL1, subsequently influencing the VIL1-dependent chromatin loop upon exposure to light, thereby modulating the genome-wide level of H3K27me3. This work represents an example in which COP1 directly regulates a chromatin regulator to orchestrate photomorphogenesis.