RESUMO
The ability of cells to perceive and translate versatile cues into differential chromatin and transcriptional states is critical for many biological processes1-5. In plants, timely transition to a flowering state is crucial for successful reproduction6-9. EARLY BOLTING IN SHORT DAY (EBS) is a negative transcriptional regulator that prevents premature flowering in Arabidopsis thaliana10,11. We found that EBS contains bivalent bromo-adjacent homology (BAH)-plant homeodomain (PHD) reader modules that bind H3K27me3 and H3K4me3, respectively. We observed co-enrichment of a subset of EBS-associated genes with H3K4me3, H3K27me3, and Polycomb repressor complex 2 (PRC2). Notably, EBS adopted an autoinhibition mode to mediate its switch in binding preference between H3K27me3 and H3K4me3. This binding balance was critical because disruption of either EBS-H3K27me3 or EBS-H3K4me3 interaction induced early floral transition. Our results identify a bivalent chromatin reader capable of recognizing two antagonistic histone marks, and we propose a distinct mechanism of interaction between active and repressive chromatin states.
Assuntos
Proteínas de Arabidopsis/genética , Arabidopsis/genética , Flores/genética , Genes Reguladores/genética , Histonas/genética , Cromatina/genética , Regulação da Expressão Gênica de Plantas/genética , Proteínas de Homeodomínio/genética , Transcrição Gênica/genéticaRESUMO
The ability of a cell to dynamically switch its chromatin between different functional states constitutes a key mechanism regulating gene expression. Histone mark "readers" display distinct binding specificity to different histone modifications and play critical roles in regulating chromatin states. Here, we show a plant-specific histone reader SHORT LIFE (SHL) capable of recognizing both H3K27me3 and H3K4me3 via its bromo-adjacent homology (BAH) and plant homeodomain (PHD) domains, respectively. Detailed biochemical and structural studies suggest a binding mechanism that is mutually exclusive for either H3K4me3 or H3K27me3. Furthermore, we show a genome-wide co-localization of SHL with H3K27me3 and H3K4me3, and that BAH-H3K27me3 and PHD-H3K4me3 interactions are important for SHL-mediated floral repression. Together, our study establishes BAH-PHD cassette as a dual histone methyl-lysine binding module that is distinct from others in recognizing both active and repressive histone marks.
