Department of Biology, Institute of Biochemistry, Carleton University, Ottawa, ON, Canada.
Department of Biological Sciences and Center for Environmental Epigenetics and Development, University of Toronto, Toronto, ON, Canada.
Mol Cell Biochem. 2020 Nov;474(1-2):229-241. doi: 10.1007/s11010-020-03848-x. Epub 2020 Jul 29.
Trachemys scripta elegans can survive up to three months of absolute anoxia at 3 °C and recover with minimal cellular damage. Red-eared sliders employ various physiological and biochemical adaptations to survive anoxia with metabolic rate depression (MRD) being the most prominent adaptation. MRD is mediated by epigenetic, transcriptional, post-transcriptional, and post-translational mechanisms aimed at shutting down cellular processes that are not needed for anoxia survival, while reprioritizing ATP towards cell processes that are vital for anaerobiosis. Histone acetylation/deacetylation are epigenetic modifications that maintain a proper balance between permissive chromatin and restricted chromatin, yet very little is known about protein regulation and enzymatic activity of the writers and erasers of acetylation during natural anoxia tolerance. As such, this study explored the interplay between transcriptional activators, histone acetyltransferases (HATs), and transcriptional repressors, sirtuins (SIRTs), along with three prominent acetyl-lysine (K) moieties of histone H3 in the liver of red-eared sliders. Western immunoblotting was used to measure acetylation levels of H3-K14, H3-K18, and H3-K56, as well as protein levels of histone H3-total, HATs, and nuclear SIRTs in the liver in response to 5 h and 20 h anoxia. Global and nuclear enzymatic activity of HATs and enzymatic activity of nuclear SIRTs were also measured. Overall, a strong suppression of HATs-mediated H3 acetylation and SIRT-mediated deacetylation was evident in the liver of red-eared sliders that could play an important role in ATP conservation as part of the overall reduction in metabolic rate.
拟穴青龟可在 3°C 下存活长达三个月的绝对缺氧期，并在最小的细胞损伤下恢复。红耳滑龟通过代谢率降低（MRD）等各种生理和生化适应来在缺氧环境中存活，MRD 是通过表观遗传、转录、转录后和翻译后机制介导的，旨在关闭细胞过程，这些过程对于缺氧存活不是必需的，同时将 ATP 重新分配到对无氧至关重要的细胞过程。组蛋白乙酰化/去乙酰化是表观遗传修饰，可维持开放染色质和封闭染色质之间的适当平衡，但对于自然缺氧耐受性期间组蛋白乙酰基转移酶（HATs）和去乙酰化酶（SIRTs）的书写酶和橡皮擦的蛋白调节和酶活性知之甚少。因此，本研究探讨了转录激活剂、组蛋白乙酰基转移酶（HATs）和转录抑制剂、沉默调节蛋白（SIRTs）之间的相互作用，以及红耳滑龟肝脏中组蛋白 H3 的三个主要乙酰化赖氨酸（K）片段。Western 免疫印迹用于测量 H3-K14、H3-K18 和 H3-K56 的乙酰化水平，以及组蛋白 H3-总蛋白、HATs 和核 SIRTs 的蛋白水平，以响应 5 小时和 20 小时缺氧。还测量了 HATs 的整体和核酶活性以及核 SIRTs 的酶活性。总的来说，红耳滑龟肝脏中 HATs 介导的 H3 乙酰化和 SIRT 介导的去乙酰化受到强烈抑制，这可能在作为整体代谢率降低的一部分的 ATP 节约中发挥重要作用。
