Department of Cell & Developmental Biology, Biocenter, University of Würzburg, Würzburg, Germany.
Quantitative Proteomics, Institute of Molecular Biology (IMB), Mainz, Germany.
PLoS Pathog. 2022 Jun 8;18(6):e1010514. doi: 10.1371/journal.ppat.1010514. eCollection 2022 Jun.
A cascade of histone acetylation events with subsequent incorporation of a histone H2A variant plays an essential part in transcription regulation in various model organisms. A key player in this cascade is the chromatin remodelling complex SWR1, which replaces the canonical histone H2A with its variant H2A.Z. Transcriptional regulation of polycistronic transcription units in the unicellular parasite Trypanosoma brucei has been shown to be highly dependent on acetylation of H2A.Z, which is mediated by the histone-acetyltransferase HAT2. The chromatin remodelling complex which mediates H2A.Z incorporation is not known and an SWR1 orthologue in trypanosomes has not yet been reported. In this study, we identified and characterised an SWR1-like remodeller complex in T. brucei that is responsible for Pol II-dependent transcriptional regulation. Bioinformatic analysis of potential SNF2 DEAD/Box helicases, the key component of SWR1 complexes, identified a 1211 amino acids-long protein that exhibits key structural characteristics of the SWR1 subfamily. Systematic protein-protein interaction analysis revealed the existence of a novel complex exhibiting key features of an SWR1-like chromatin remodeller. RNAi-mediated depletion of the ATPase subunit of this complex resulted in a significant reduction of H2A.Z incorporation at transcription start sites and a subsequent decrease of steady-state mRNA levels. Furthermore, depletion of SWR1 and RNA-polymerase II (Pol II) caused massive chromatin condensation. The potential function of several proteins associated with the SWR1-like complex and with HAT2, the key factor of H2A.Z incorporation, is discussed.
组蛋白乙酰化事件的级联反应，随后将组蛋白 H2A 变体纳入其中，在各种模式生物的转录调控中起着至关重要的作用。在这个级联反应中，关键参与者是染色质重塑复合物 SWR1，它用其变体 H2A.Z 取代经典的组蛋白 H2A。单细胞寄生虫布鲁氏锥虫多顺反子转录单位的转录调控被证明高度依赖于 H2A.Z 的乙酰化，这是由组蛋白乙酰转移酶 HAT2 介导的。介导 H2A.Z 纳入的染色质重塑复合物尚不清楚，并且尚未报道锥虫中的 SWR1 同源物。在这项研究中，我们在 T. brucei 中鉴定和表征了一种介导 H2A.Z 纳入的 SWR1 样重塑复合物，该复合物负责 Pol II 依赖性转录调控。对潜在的 SNF2 DEAD/Box 解旋酶（SWR1 复合物的关键组成部分）的生物信息学分析，确定了一种 1211 个氨基酸长的蛋白质，它表现出 SWR1 亚家族的关键结构特征。系统的蛋白质-蛋白质相互作用分析揭示了一种新型复合物的存在，该复合物表现出 SWR1 样染色质重塑复合物的关键特征。该复合物的 ATP 酶亚基的 RNAi 介导耗尽导致转录起始位点处 H2A.Z 纳入的显著减少，以及稳态 mRNA 水平的随后降低。此外，SWR1 和 RNA 聚合酶 II（Pol II）的耗竭导致大量染色质凝聚。讨论了与 SWR1 样复合物以及与 H2A.Z 纳入的关键因素 HAT2 相关的几种蛋白质的潜在功能。
