Laboratory of Plant Molecular Physiology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan.
Gene Discovery Research Group, RIKEN Center for Sustainable Resource Science, Yokohama, Kanagawa 230-0045, Japan.
Proc Natl Acad Sci U S A. 2017 Oct 3;114(40):E8528-E8536. doi: 10.1073/pnas.1704189114. Epub 2017 Sep 18.
DEHYDRATION-RESPONSIVE ELEMENT BINDING PROTEIN 2A (DREB2A) acts as a key transcription factor in both drought and heat stress tolerance in and induces the expression of many drought- and heat stress-inducible genes. Although expression itself is induced by stress, the posttranslational regulation of DREB2A, including protein stabilization, is required for its transcriptional activity. The deletion of a 30-aa central region of DREB2A known as the negative regulatory domain (NRD) transforms DREB2A into a stable and constitutively active form referred to as DREB2A CA. However, the molecular basis of this stabilization and activation has remained unknown for a decade. Here we identified BTB/POZ AND MATH DOMAIN proteins (BPMs), substrate adaptors of the Cullin3 (CUL3)-based E3 ligase, as DREB2A-interacting proteins. We observed that DREB2A and BPMs interact in the nuclei, and that the NRD of DREB2A is sufficient for its interaction with BPMs. -knockdown plants exhibited increased DREB2A accumulation and induction of DREB2A target genes under heat and drought stress conditions. Genetic analysis indicated that the depletion of expression conferred enhanced thermotolerance via DREB2A stabilization. Thus, the BPM-CUL3 E3 ligase is likely the long-sought factor responsible for NRD-dependent DREB2A degradation. Through the negative regulation of DREB2A stability, BPMs modulate the heat stress response and prevent an adverse effect of excess DREB2A on plant growth. Furthermore, we found the BPM recognition motif in various transcription factors, implying a general contribution of BPM-mediated proteolysis to divergent cellular responses via an accelerated turnover of transcription factors.
脱水应答元件结合蛋白 2A（DREB2A）作为一个关键的转录因子，在干旱和热胁迫耐受中发挥作用，并诱导许多干旱和热胁迫诱导基因的表达。尽管 DREB2A 的表达本身受到胁迫的诱导，但 DREB2A 的翻译后调节，包括蛋白质稳定化，对于其转录活性是必需的。DREB2A 中称为负调节域（NRD）的 30 个氨基酸中央区域的缺失将 DREB2A 转化为一种稳定且组成型激活的形式，称为 DREB2A CA。然而，这种稳定化和激活的分子基础在十年内仍然未知。在这里，我们鉴定了 BTB/POZ 和 MATH 结构域蛋白（BPMs），作为 Cullin3（CUL3）-基础 E3 连接酶的底物衔接蛋白，作为 DREB2A 相互作用蛋白。我们观察到 DREB2A 和 BPMs 在核内相互作用，并且 DREB2A 的 NRD 足以与其相互作用。-敲低植物在热和干旱胁迫条件下表现出 DREB2A 积累增加和 DREB2A 靶基因的诱导。遗传分析表明，表达的耗尽通过 DREB2A 稳定化赋予了增强的耐热性。因此，BPM-CUL3 E3 连接酶可能是长期以来负责 NRD 依赖性 DREB2A 降解的因子。通过 DREB2A 稳定性的负调控，BPMs 调节热应激反应，并防止过量 DREB2A 对植物生长的不利影响。此外，我们在各种转录因子中发现了 BPM 识别基序，这意味着 BPM 介导的蛋白水解通过转录因子的快速周转对不同的细胞反应有一般的贡献。
