From yeast to human, the Spt-Ada-GCN5-acetyltransferase (SAGA) gigantic complex modifies chromatin during RNA polymerase II initiation and elongation steps to facilitate transcription. Its enzymatic activity involves a histone acetyltransferase module (HATm) that acetylates multiple lysine residues on the N-terminal tails of histones H2B and H3 and a deubiquitination module (DUBm) that triggers co-transcriptional deubiquitination of histone H2B. With a few notable exceptions described in this review, most SAGA subunits identified in yeast and metazoa are present in plants. Studies from the last 20 years have unveiled that different SAGA subunits are involved in gene expression regulation during the plant life cycle and in response to various types of stress or environmental cues. Their functional analysis in the Arabidopsis thaliana model species is increasingly shedding light on their intrinsic properties and how they can themselves be regulated during plant adaptive responses. Recent biochemical studies have also uncovered multiple associations between plant SAGA and chromatin machineries linked to RNA pol II transcription. Still, considerably less is known about the molecular links between SAGA or SAGA-like complexes and chromatin dynamics during transcription in Arabidopsis and other plant species. We summarize the emerging knowledge on plant SAGA complex composition and activity, with a particular focus on the best-characterized subunits from its HAT (such as GCN5) and DUB (such as UBP22) modules, and implication of these ensembles in plant development and adaptive responses.

从酵母到人，Spt-Ada-GCN5-乙酰基转移酶（SAGA）巨大的复合物在RNA聚合酶II的起始和延伸步骤中修饰染色质，以促进转录。它的酶活性涉及一个组蛋白乙酰转移酶模块（HATm），该模块乙酰化组蛋白H2B和H3的N末端尾巴上的多个赖氨酸残基，以及一个脱泛素化模块（DUBm），触发组蛋白H2B的共转录去泛素化。除了这篇综述中描述的几个显着例外，酵母和后生动物中鉴定出的大多数SAGA亚基都存在于植物中。过去20年的研究表明，不同的SAGA亚基在植物的生命周期以及对各种胁迫或环境因素的响应中均参与基因表达调控。他们的功能分析拟南芥模型种越来越多地揭示其内在特性以及如何在植物适应性反应中对其自身进行调控。最近的生化研究还发现了植物SAGA和与RNA pol II转录相关的染色质机制之间的多种关联。然而，关于拟南芥和其他植物物种转录过程中SAGA或SAGA样复合物与染色质动力学之间的分子联系知之甚少。我们总结了关于植物SAGA复合物的组成和活性的新兴知识，尤其关注其HAT（如GCN5）和DUB（如UBP22）模块中最典型的亚基，以及这些集合对植物发育和适应性的影响。回应。