Dynamics of polycomb proteins-mediated histone modifications during UV irradiation-induced DNA damage

Abstract Polycomb group (PcG) complexes are known to be chromatin modifiers and transcriptional repressors. In this work, we reported that the histone-modifying PcG complexes are able to participate in the repair process of ultraviolet (UV)-induced DNA lesions in the silkworm, Bombyx mori . The silkworm cells with depletion of PcG genes showed hypersensitive to UV–C irradiation and increased inhibition of cell proliferation. Interestingly, an SQ site in the silkworm-human chimeric H2A protein synthesized here was phosphorylated rapidly upon UV–C exposure, which could be used as a marker for monitoring the response to DNA damage in silkworm cells. Under these UV–C irradiated conditions, we found that PRC1-mediated ubiquitylation of H2AX, but not of H2AZ, were decreased and this deubiquitylation was independent of its phosphorylation event. In contrast, UV–C irradiation induced the increase of trimethylation of lysine 27 on histone H3 (H3K27me3), a mark of transcriptionally silent chromatin catalyzed by another PcG subcomplex, PRC2. Collectively, we provided the first evidence on chromatin remodeling in response to UV–C lesion in silkworm and revealed another layer role for PcG complexes-mediated histone modifications in contributing to creating an open chromatin structure for the efficient repair of DNA damages.