Institut de Biologie de l'ENS (IBENS), Département de Biologie, École Normale Supérieure, CNRS, INSERM, Université PSL, Paris, 75005, France.
CNRS UMR6286, UFIP UFR Sciences et Techniques, Université de Nantes, 2 rue de la Houssinière 44322, Nantes Cedex 03, France.
New Phytol. 2021 Mar;229(6):3208-3220. doi: 10.1111/nph.17129. Epub 2020 Dec 31.
In multicellular organisms, Polycomb Repressive Complex2 (PRC2) is known to deposit tri-methylation of lysine 27 of histone H3 (H3K27me3) to establish and maintain gene silencing, critical for developmentally regulated processes. The PRC2 complex is absent in both widely studied model yeasts, which initially suggested that PRC2 arose with the emergence of multicellularity. However, its discovery in several unicellular species including microalgae questions its role in unicellular eukaryotes. Here, we use Phaeodactylum tricornutum enhancer of zeste E(z) knockouts and show that P. tricornutum E(z) is responsible for di- and tri-methylation of lysine 27 of histone H3. H3K27me3 depletion abolishes cell morphology in P. tricornutum providing evidence for its role in cell differentiation. Genome-wide profiling of H3K27me3 in fusiform and triradiate cells further revealed genes that may specify cell identity. These results suggest a role for PRC2 and its associated mark in cell differentiation in unicellular species, and highlight their ancestral function in a broader evolutionary context than currently is appreciated.
在多细胞生物中，多梳抑制复合物 2（PRC2）被认为能将组蛋白 H3 赖氨酸 27 三甲基化（H3K27me3），从而建立和维持基因沉默，这对发育调控过程至关重要。这一复合物在两种广泛研究的模式酵母中均不存在，这最初表明 PRC2 是随着多细胞生物的出现而产生的。然而，它在几种单细胞生物中的发现，包括微藻，使其在单细胞真核生物中的作用受到质疑。在这里，我们使用三角褐指藻增强子的锌指 E(z) 敲除突变体，并表明三角褐指藻 E(z) 负责组蛋白 H3 赖氨酸 27 的二甲基化和三甲基化。H3K27me3 的耗竭会破坏三角褐指藻的细胞形态，为其在细胞分化中的作用提供了证据。在梭形和辐射状细胞中的 H3K27me3 的全基因组分析进一步揭示了可能指定细胞身份的基因。这些结果表明 PRC2 及其相关标记在单细胞物种中的细胞分化中具有作用，并强调了它们在更广泛的进化背景下的古老功能，这比目前人们所理解的更为广泛。
