Tvardovskiy Andrey, Schwämmle Veit, Kempf Stefan J, Rogowska-Wrzesinska Adelina, Jensen Ole N
Department of Biochemistry and Molecular Biology, VILLUM Center for Bioanalytical Sciences, University of Southern Denmark, Campusvej 55, DK-5230 Odense M, Denmark.
Center for Epigenetics, University of Southern Denmark, Campusvej 55, DK-5230 Odense M, Denmark.
Nucleic Acids Res. 2017 Sep 19;45(16):9272-9289. doi: 10.1093/nar/gkx696.
Deposition of replication-independent histone variant H3.3 into chromatin is essential for many biological processes, including development and reproduction. Unlike replication-dependent H3.1/2 isoforms, H3.3 is expressed throughout the cell cycle and becomes enriched in postmitotic cells with age. However, lifelong dynamics of H3 variant replacement and the impact of this process on chromatin organization remain largely undefined. Using quantitative middle-down proteomics we demonstrate that H3.3 accumulates to near saturation levels in the chromatin of various mouse somatic tissues by late adulthood. Accumulation of H3.3 is associated with profound changes in global levels of both individual and combinatorial H3 methyl modifications. A subset of these modifications exhibit distinct relative abundances on H3 variants and remain stably enriched on H3.3 throughout the lifespan, suggesting a causal relationship between H3 variant replacement and age-dependent changes in H3 methylation. Furthermore, the H3.3 level is drastically reduced in human hepatocarcinoma cells as compared to nontumoral hepatocytes, suggesting the potential utility of the H3.3 relative abundance as a biomarker of abnormal cell proliferation activity. Overall, our study provides the first quantitative characterization of dynamic changes in H3 proteoforms throughout lifespan in mammals and suggests a role for H3 variant replacement in modulating H3 methylation landscape with age.
不依赖复制的组蛋白变体H3.3沉积到染色质中对许多生物学过程至关重要，包括发育和繁殖。与依赖复制的H3.1/2亚型不同，H3.3在整个细胞周期中都有表达，并随着年龄的增长在有丝分裂后的细胞中富集。然而，H3变体替换的终身动态变化以及这一过程对染色质组织的影响在很大程度上仍不明确。我们使用定量的中向下蛋白质组学方法证明，到成年后期，H3.3在各种小鼠体细胞组织的染色质中积累到接近饱和水平。H3.3的积累与单个和组合的H3甲基化修饰的整体水平的深刻变化有关。这些修饰中的一部分在H3变体上表现出不同的相对丰度，并在整个生命周期中在H3.3上保持稳定富集，这表明H3变体替换与H3甲基化的年龄依赖性变化之间存在因果关系。此外，与非肿瘤性肝细胞相比，人肝癌细胞中的H3.3水平急剧降低，这表明H3.3相对丰度作为异常细胞增殖活动生物标志物的潜在用途。总体而言，我们的研究首次对哺乳动物整个生命周期中H3蛋白质形式的动态变化进行了定量表征，并表明H3变体替换在随着年龄调节H3甲基化格局中发挥作用。
