Iron-Binding E3 Ligase Mediates Iron Response in Plants by Targeting Basic Helix-Loop-Helix Transcription Factors
Iron-Binding E3 Ligase Mediates Iron Response in Plants by Targeting Basic Helix-Loop-Helix Transcription Factors
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DOI：
10.1104/pp.114.250837
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发表时间：
2015-01-01
期刊：
影响因子：
7.4
通讯作者：
Long, Terri A.
中科院分区：
文献类型：
--
作者：
Selote, Devarshi;Samira, Rozalynne;Long, Terri A.
植物和动物中铁的吸收和代谢都受到严格调节。在拟南芥中，BRUTUS (BTS) 包含三个血红蛋白 (HHE) 结构域和一个真正有趣的新基因 (RING) 结构域，与碱性螺旋-环-螺旋转录因子相互作用，这些转录因子能够与缺铁反应的正调节因子 POPEYE (PYE) 形成异二聚体。 BTS 已被证明具有 E3 连接酶能力，并在根系生长、根际酸化和缺铁时的铁还原酶活性中发挥作用。为了进一步表征该蛋白的功能，我们检查了重组ProBTS::b-葡萄糖醛酸酶的表达模式，发现它在发育中的胚胎和其他生殖组织中表达，与其在生殖生长和发育中的明显作用相对应。我们的研究结果还表明，BTS 和 PYE 样 (PYEL) 碱性螺旋-环-螺旋转录因子之间的相互作用发生在细胞核内，并且依赖于 RING 结构域的存在。我们提供的证据表明，在没有铁的情况下，BTS 可促进 26S 蛋白酶体介导的 PYEL 蛋白降解。我们还确定，在 HHE 结构域结合铁后，BTS 就会不稳定，并且这种不稳定依赖于 HHE 结构域内的特定残基。这项研究揭示了植物铁稳态的一个重要而独特的机制，E3泛素连接酶可以通过翻译后控制参与缺铁反应的转录调控网络的组成部分。
Iron uptake and metabolism are tightly regulated in both plants and animals. In Arabidopsis ( Arabidopsis thaliana), BRUTUS ( BTS), which contains three hemerythrin ( HHE) domains and a Really Interesting New Gene ( RING) domain, interacts with basic helix- loop- helix transcription factors that are capable of forming heterodimers with POPEYE ( PYE), a positive regulator of the iron deficiency response. BTS has been shown to have E3 ligase capacity and to play a role in root growth, rhizosphere acidification, and iron reductase activity in response to iron deprivation. To further characterize the function of this protein, we examined the expression pattern of recombinant ProBTS:: b- GLUCURONIDASE and found that it is expressed in developing embryos and other reproductive tissues, corresponding with its apparent role in reproductive growth and development. Our findings also indicate that the interactions between BTS and PYE- like ( PYEL) basic helix- loop- helix transcription factors occur within the nucleus and are dependent on the presence of the RING domain. We provide evidence that BTS facilitates 26S proteasome- mediated degradation of PYEL proteins in the absence of iron. We also determined that, upon binding iron at the HHE domains, BTS is destabilized and that this destabilization relies on specific residues within the HHE domains. This study reveals an important and unique mechanism for plant iron homeostasis whereby an E3 ubiquitin ligase may posttranslationally control components of the transcriptional regulatory network involved in the iron deficiency response.