The repressive role of H2A.Z variant in transcriptional regulation depends on AtBMI1 activity in Arabidopsis

H2A.Z variant has emerged as a critical player in regulating plant responses to environment; however, the mechanism by which H2A.Z mediates this regulation remains unclear. In Arabidopsis, H2A.Z has been proposed to have opposite effects on transcription depending on its localization within the gene. These opposite roles have been assigned by correlating gene expression and H2A.Z enrichment analyses but without considering the impact of possible H2A.Z posttranslational modifications. Here we show that H2A.Z can be monoubiquitinated by the PRC1 components AtBMI1A/B/C. The incorporation of this modification is required for H2A.Z-mediated transcriptional repression through a mechanism that does not require PRC2 activity. Our data suggest that the dual role of H2A.Z in regulating gene expression depends on the modification that it carries, while the levels of H2A.Z within genes depend on the transcriptional activity. mRNA profiles of 7DAG Arabidopsis seedlings Col-0; doble mutant hta9hta11 ; hta9hta11_FLAG-HTA9_N, hta9hta11_FLAG-HTA9_RR and weak double mutant atbmi1ab_weak

组蛋白H2A.Z变体（H2A.Z variant）已成为调控植物环境响应的关键因子，然而H2A.Z介导该调控过程的具体分子机制仍不明晰。在拟南芥（Arabidopsis）中，已有研究提出H2A.Z对基因转录的调控作用具有双重性，这取决于其在基因内部的定位。这类双重功能的界定最初是通过关联基因表达与H2A.Z富集分析得出的，但未考虑H2A.Z可能存在的翻译后修饰（posttranslational modifications）所带来的影响。本研究证实，H2A.Z可被多梳抑制复合体1（PRC1）的组分AtBMI1A/B/C催化单泛素化修饰（monoubiquitination）。该修饰的引入对于H2A.Z介导的转录抑制过程是必需的，且其调控机制不依赖于多梳抑制复合体2（PRC2）的活性。本研究数据表明，H2A.Z在调控基因表达中的双重功能取决于其所携带的修饰类型，而基因内H2A.Z的富集水平则与转录活性密切相关。本研究的分析对象为7DAG拟南芥幼苗的mRNA表达谱，涉及的材料包括野生型Col-0、双突变体hta9hta11、互补株系hta9hta11_FLAG-HTA9_N、hta9hta11_FLAG-HTA9_RR以及弱效双突变体atbmi1ab_weak。