组蛋白2B泛素化(H2Bub)和H3在赖氨酸4(H3K4me3)的三甲基化与转录激活相关。然而,这些修饰在植物转录中的功能在很大程度上仍然未知。这里,我们报告了H2Bub和H3K4me3沉积与RNA聚合酶相关因子VERNALIZATIONINCE2(VIP2)与花斑C(FLC)结合的协调调节拟南芥的开花时间。我们发现RING结构域蛋白组蛋白单定量1(HUB1)和HUB2(我们称为HUB1/2),它们负责H2Bub,与阿拉伯三讲机相互作用(ATX1),这是H3K4me3沉积所需的,促进FLC的转录并抑制开花时间。FRIGIDIA(FRI)背景中的atx1-2hub1-10hubb2-2三重突变体显示出像FRIhub1-10hubb2-2一样的早期开花,而ATX1的过表达未能挽救hub1-10hubb2-2的早期开花表型。HUB1和HUB2的突变降低了FLC的ATX1富集,表明在FLC中ATX1募集和H3K4me3沉积需要HUB1和HUB2。我们还发现,VIP2直接与HUB1,HUB2和ATX1结合,并且FRIhub1-10hubb2-2和FRIatx1-2植物中VIP2的丢失导致早期开花,就像FRIvip2-10中观察到的那样。HUB2和ATX1功能丧失受损的FLCVIP2富集,并降低了FLC的转录起始和延伸。此外,VIP2中的突变降低了FLC的HUB1和ATX1富集以及H2Bub和H3K4me3水平。一起,我们的研究结果表明,HUB1/2,ATX1和VIP2协同调节H2Bub和H3K4me3沉积,FLC转录,开花时间。
Histone 2B ubiquitination (H2Bub) and trimethylation of H3 at lysine 4 (H3K4me3) are associated with transcription activation. However, the function of these modifications in transcription in plants remains largely unknown. Here, we report that coordination of H2Bub and H3K4me3 deposition with the binding of the RNA polymerase-associated factor VERNALIZATION INDEPENDENCE2 (VIP2) to FLOWERING LOCUS C (
FLC) modulates flowering time in Arabidopsis. We found that RING domain protein HISTONE MONOUBIQUITINATION1 (HUB1) and HUB2 (we refer as HUB1/2), which are responsible for H2Bub, interact with ARABIDOPSIS TRITHORAX1 (ATX1), which is required for H3K4me3 deposition, to promote the transcription of FLC and repress the flowering time. The atx1-2 hub1-10 hub2-2 triple mutant in FRIGIDIA (FRI) background displayed early flowering like FRI hub1-10 hub2-2 and overexpression of ATX1 failed to rescue the early flowering phenotype of hub1-10 hub2-2. Mutations in HUB1 and HUB2 reduced the ATX1 enrichment at
FLC, indicating that HUB1 and HUB2 are required for ATX1 recruitment and H3K4me3 deposition at
FLC. We also found that the VIP2 directly binds to HUB1, HUB2, and ATX1 and that loss of VIP2 in FRI hub1-10 hub2-2 and FRI atx1-2 plants resulted in early flowering like that observed in FRI vip2-10. Loss of function of HUB2 and ATX1 impaired VIP2 enrichment at FLC, and reduced the transcription initiation and elongation of
FLC. In addition, mutations in VIP2 reduced HUB1 and ATX1 enrichment and H2Bub and H3K4me3 levels at
FLC. Together, our findings revealed that HUB1/2, ATX1, and VIP2 coordinately modulate H2Bub and H3K4me3 deposition, FLC transcription, and flowering time.