Riaz Sadaf, Sui Zhenghong, Niaz Zeeshan, Khan Sohrab, Liu Yuan, Liu Haoxin
Key Laboratory of Marine Genetics and Breeding (Ocean University of China), Ministry of Education, Qingdao, 266003, China.
Department of Microbiology, University of Veterinary and Animal Sciences, Lahore 54000, Pakistan.
Microorganisms. 2018 Dec 14;6(4):128. doi: 10.3390/microorganisms6040128.
Dinoflagellates are important eukaryotic microorganisms that play critical roles as producers and grazers, and cause harmful algal blooms. The unusual nuclei of dinoflagellates "dinokaryon" have led researchers to investigate their enigmatic nuclear features. Their nuclei are unusual in terms of their permanently condensed nucleosome-less chromatin, immense genome, low protein to DNA ratio, guanine-cytosine rich methylated DNA, and unique mitosis process. Furthermore, dinoflagellates are the only known group of eukaryotes that apparently lack histone proteins. Over the course of evolution, dinoflagellates have recruited other proteins, e.g., histone-like proteins (HLPs), from bacteria and dinoflagellates/viral nucleoproteins (DVNPs) from viruses as histone substitutes. Expression diversity of these nucleoproteins has greatly influenced the chromatin structure and gene expression regulation in dinoflagellates. Histone replacement proteins (HLPs and DVNPs) are hypothesized to perform a few similar roles as histone proteins do in other eukaryotes, i.e., gene expression regulation and repairing DNA. However, their role in bulk packaging of DNA is not significant as low amounts of proteins are associated with the gigantic genome. This review intends to summarize the discoveries encompassing unique nuclear features of dinoflagellates, particularly focusing on histone and histone replacement proteins. In addition, a comprehensive view of the evolution of dinoflagellate nuclei is presented.
甲藻是重要的真核微生物，作为生产者和食草动物发挥着关键作用，并会引发有害藻华。甲藻不同寻常的细胞核“双鞭毛核”促使研究人员去探究其神秘的核特征。它们的细胞核在以下方面显得不同寻常：永久浓缩的无核小体染色质、巨大的基因组、低蛋白质与DNA比例、富含鸟嘌呤 - 胞嘧啶的甲基化DNA以及独特的有丝分裂过程。此外，甲藻是唯一已知的明显缺乏组蛋白的真核生物类群。在进化过程中，甲藻从细菌中招募了其他蛋白质，如组蛋白样蛋白（HLP），并从病毒中获取了甲藻/病毒核蛋白（DVNP）作为组蛋白替代物。这些核蛋白的表达多样性极大地影响了甲藻的染色质结构和基因表达调控。据推测，组蛋白替代蛋白（HLP和DVNP）在甲藻中发挥着与其他真核生物中组蛋白类似的一些作用，即基因表达调控和DNA修复。然而，由于与巨大的基因组相关联的蛋白质数量较少，它们在DNA的整体包装中的作用并不显著。本综述旨在总结有关甲藻独特核特征的发现，特别关注组蛋白和组蛋白替代蛋白。此外，还呈现了甲藻细胞核进化的全面观点。
