Department of Chemistry and Biology, Ryerson University, 350 Victoria St., Toronto, M5B 2K3, Canada.
Donnelly Centre, University of Toronto, Toronto, M5S 3E1, Canada.
Sci Rep. 2020 Jan 13;10(1):168. doi: 10.1038/s41598-019-56867-0.
Chromatin organization influences most aspects of gene expression regulation. The linker histone H1, along with the core histones, is a key component of eukaryotic chromatin. Despite its critical roles in chromatin structure and function and gene regulation, studies regarding the H1 protein-protein interaction networks, particularly outside of Opisthokonts, are limited. The nuclear dimorphic ciliate protozoan Tetrahymena thermophila encodes two distinct nucleus-specific linker histones, macronuclear Hho1 and micronuclear Mlh1. We used a comparative proteomics approach to identify the Hho1 and Mlh1 protein-protein interaction networks in Tetrahymena during growth, starvation, and sexual development. Affinity purification followed by mass spectrometry analysis of the Hho1 and Mlh1 proteins revealed a non-overlapping set of co-purifying proteins suggesting that Tetrahymena nucleus-specific linker histones are subject to distinct regulatory pathways. Furthermore, we found that linker histones interact with distinct proteins under the different stages of the Tetrahymena life cycle. Hho1 and Mlh1 co-purified with several Tetrahymena-specific as well as conserved interacting partners involved in chromatin structure and function and other important cellular pathways. Our results suggest that nucleus-specific linker histones might be subject to nucleus-specific regulatory pathways and are dynamically regulated under different stages of the Tetrahymena life cycle.
染色质组织影响基因表达调控的大多数方面。连接组蛋白 H1 与核心组蛋白一起，是真核染色质的关键组成部分。尽管 H1 蛋白在染色质结构和功能以及基因调控中具有重要作用，但关于其蛋白质-蛋白质相互作用网络的研究，特别是在后生动物之外的研究是有限的。核二形纤毛虫原生动物嗜热四膜虫编码两种不同的核特异性连接组蛋白，大核 Hho1 和小核 Mlh1。我们使用比较蛋白质组学方法来鉴定嗜热四膜虫在生长、饥饿和有性发育过程中 Hho1 和 Mlh1 的蛋白质-蛋白质相互作用网络。Hho1 和 Mlh1 蛋白的亲和纯化后进行质谱分析，揭示了一组非重叠的共纯化蛋白，表明嗜热四膜虫核特异性连接组蛋白受到不同的调控途径的影响。此外，我们发现，在嗜热四膜虫生命周期的不同阶段，连接组蛋白与不同的蛋白质相互作用。Hho1 和 Mlh1 与几种嗜热四膜虫特异性以及保守的相互作用伙伴共纯化，这些伙伴参与染色质结构和功能以及其他重要的细胞途径。我们的结果表明，核特异性连接组蛋白可能受到核特异性调控途径的影响，并在嗜热四膜虫生命周期的不同阶段受到动态调控。
