Schlesinger Sharon, Kaffe Binyamin, Melcer Shai, Aguilera Jose D, Sivaraman Divya M, Kaplan Tommy, Meshorer Eran
The Department of Genetics, The Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Jerusalem 9190401, Israel.
Department of animal science, The Robert H. Smith Faculty of Agriculture, Food, and Environment, The Hebrew University of Jerusalem, Rehovot 7610001, Israel.
Nucleic Acids Res. 2017 Dec 1;45(21):12181-12194. doi: 10.1093/nar/gkx817.
Histone variants and their chaperones are key regulators of eukaryotic transcription, and are critical for normal development. The histone variant H3.3 has been shown to play important roles in pluripotency and differentiation, and although its genome-wide patterns have been investigated, little is known about the role of its dynamic turnover in transcriptional regulation. To elucidate the role of H3.3 dynamics in embryonic stem cell (ESC) biology, we generated mouse ESC lines carrying a single copy of a doxycycline (Dox)-inducible HA-tagged version of H3.3 and monitored the rate of H3.3 incorporation by ChIP-seq at varying time points following Dox induction, before and after RA-induced differentiation. Comparing H3.3 turnover profiles in ESCs and RA-treated cells, we identified a hyperdynamic H3.3-containing nucleosome at the -1 position in promoters of genes expressed in ESCs. This dynamic nucleosome is restricted and shifted downstream into the +1 position following differentiation. We suggest that histone turnover dynamics provides an additional mechanism involved in expression regulation, and that a hyperdynamic -1 nucleosome marks promoters in ESCs. Our data provide evidence for regional regulation of H3.3 turnover in ESC promoters, and calls for testing, in high resolution, the dynamic behavior of additional histone variants and other structural chromatin proteins.
组蛋白变体及其伴侣蛋白是真核生物转录的关键调节因子，对正常发育至关重要。组蛋白变体H3.3已被证明在多能性和分化中发挥重要作用，尽管其全基因组模式已被研究，但关于其动态周转在转录调控中的作用知之甚少。为了阐明H3.3动态变化在胚胎干细胞（ESC）生物学中的作用，我们构建了携带单拷贝强力霉素（Dox）诱导的HA标签化H3.3的小鼠ESC系，并在RA诱导分化前后的不同时间点通过ChIP-seq监测Dox诱导后H3.3的掺入率。比较ESC和RA处理细胞中的H3.3周转谱，我们在ESC中表达的基因启动子的 -1位置鉴定出一个含有高动态H3.3的核小体。这种动态核小体在分化后受到限制并向下游移动到 +1位置。我们认为组蛋白周转动态提供了一种参与表达调控的额外机制，并且高动态的 -1核小体标记ESC中的启动子。我们的数据为ESC启动子中H3.3周转的区域调控提供了证据，并呼吁以高分辨率测试其他组蛋白变体和其他结构染色质蛋白的动态行为。
