Alcázar-Román Abel R, Wente Susan R
Department of Cell and Developmental Biology, Vanderbilt University Medical Center, U-3209 MRBIII, 465 21st Avenue South, Nashville, TN 37232-8240, USA.
Chromosoma. 2008 Feb;117(1):1-13. doi: 10.1007/s00412-007-0126-4. Epub 2007 Oct 18.
Highly phosphorylated, soluble inositides are an emerging family of potential eukaryotic second messengers. The mechanisms for generating an outstanding diversity of mono- and pyrophosphorylated inositides have been recently elucidated and require a series of conserved lipases, kinases, and phosphatases. With several of the inositol kinases and the phospholipase C having access to the nucleus, roles for inositides in nuclear functions have been suggested. In support of this hypothesis, multiple studies have revealed the protein machines that are modulated by these inositides and found specific roles in nuclear physiology. In this paper, we review a novel paradigm for regulating gene expression at distinct steps by different inositide isomers. We discuss discoveries showing inositol polyphosphate regulation of gene expression at the level of transcription, chromatin remodeling, messenger ribonucleic acid (mRNA) editing, and mRNA export. Recent structural studies of inositol polyphosphate-binding proteins suggest the inositides modulate protein function as essential structural cofactors, triggers for allosteric or induced fit structural changes, and direct antagonistic competitors for other inositide ligands. We propose that the cell orchestrates the localized production of soluble inositol polyphosphates and inositol pyrophosphates to direct decisive and rapid signaling events. These insights also illustrate how extracellular stimuli might faithfully trigger the correct synchrony between gene expression steps and coordinate nuclear responses to changes in cellular environments.
高度磷酸化的可溶性肌醇磷脂是一类新兴的潜在真核生物第二信使家族。近期已阐明生成单磷酸化和焦磷酸化肌醇磷脂显著多样性的机制,这需要一系列保守的脂肪酶、激酶和磷酸酶。由于几种肌醇激酶和磷脂酶C能够进入细胞核,因此有人提出肌醇磷脂在核功能中发挥作用。为支持这一假设,多项研究揭示了受这些肌醇磷脂调节的蛋白质机器,并发现了它们在核生理学中的特定作用。在本文中,我们综述了一种新的模式,即不同的肌醇磷脂异构体在不同步骤调节基因表达。我们讨论了有关肌醇多磷酸在转录、染色质重塑、信使核糖核酸(mRNA)编辑和mRNA输出水平调节基因表达的发现。近期对肌醇多磷酸结合蛋白的结构研究表明,肌醇磷脂作为必需的结构辅助因子调节蛋白质功能,是变构或诱导契合结构变化的触发因素,也是其他肌醇磷脂配体的直接拮抗竞争者。我们提出,细胞精心安排可溶性肌醇多磷酸和肌醇焦磷酸的局部产生,以指导决定性和快速的信号事件。这些见解还说明了细胞外刺激如何忠实地触发基因表达步骤之间的正确同步,并协调细胞核对细胞环境变化的反应。