MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK.
John Innes Centre, Norwich Research Park, Norwich NR4 7UH, UK.
Cell Rep. 2022 Nov 8;41(6):111607. doi: 10.1016/j.celrep.2022.111607.
Transcriptional silencing through the Polycomb silencing machinery utilizes a "read-write" mechanism involving histone tail modifications. However, nucleation of silencing and long-term stable transmission of the silenced state also requires P-olycomb Repressive Complex 2 (PRC2) accessory proteins, whose molecular role is poorly understood. The Arabidopsis VEL proteins are accessory proteins that interact with PRC2 to nucleate and propagate silencing at the FLOWERING LOCUS C (FLC) locus, enabling early flowering in spring. Here, we report that VEL proteins contain a domain related to an atypical four-helix bundle that engages in spontaneous concentration-dependent head-to-tail polymerization to assemble dynamic biomolecular condensates. Mutations blocking polymerization of this VEL domain prevent Polycomb silencing at FLC. Plant VEL proteins thus facilitate assembly of dynamic multivalent Polycomb complexes required for inheritance of the silenced state.
通过 Polycomb 沉默机制的转录沉默利用了一种涉及组蛋白尾部修饰的“读写”机制。然而，沉默的起始和沉默状态的长期稳定传递也需要多梳抑制复合物 2 (PRC2)辅助蛋白，其分子作用知之甚少。拟南芥 VEL 蛋白是与 PRC2 相互作用的辅助蛋白，可在开花时间基因 FLOWERING LOCUS C (FLC) 位点起始和传播沉默，从而使植物在春季提前开花。在这里，我们报告称，VEL 蛋白包含一个与非典型四螺旋束相关的结构域，该结构域能够自发地进行浓度依赖性的从头至尾聚合，以组装动态生物分子凝聚物。阻止该 VEL 结构域聚合的突变会阻止 FLC 处的 Polycomb 沉默。因此，植物 VEL 蛋白促进了动态多价 Polycomb 复合物的组装，这对于沉默状态的遗传是必需的。
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