Regulation and function of mammalian HSF4 in vivo

描述（由申请人提供）：哺乳动物热休克转录因子（Hsfs）的功能随着最近一代缺乏hsfl或hsf2的小鼠变得越来越清晰。这些动物模型的分析结果是惊人的，表明Hsfs在细胞凋亡、分化和发育以及维持组织稳态中的作用。为了了解hsf在体内的功能，我们培育了hsfl和hsf2敲除小鼠，现在正在努力培育不表达hsf4的小鼠。hsfl的破坏阐明了它在调节细胞凋亡和控制耐热性和雌性不育中的重要性。相反，hsf2基因敲除小鼠表现出中枢神经系统发育缺陷和精子发生减少。我们进一步证明，hsfl和hsf2的缺失会导致协同效应和缺陷，这些缺陷比单个hsf缺陷小鼠表现出的更严重。这些缺陷与大脑和行为异常、精子发生完全中断和男性不育以及其他疾病有关。与Hsfl和Hsf2相比，人们对哺乳动物Hsf家族中仅存的成员Hsf4知之甚少。Hsf4与其他hsf有几个不同之处。它以两种选择性剪接的变体形式表达，一种形式是转录激活因子，另一种形式是转录抑制因子，这两种变体在不同的组织中表达不同。我们发现Hsf4被磷酸化，并且发现了一种新的磷酸酶（命名为DSPH4），它含有双特异性酪氨酸/丝氨酸/苏氨酸磷酸酶的特征基元，可以与Hsf4结合并调节其磷酸化状态、DNA结合能力和核定位。这代表了细胞外信号调控Hsf4活性的可能机制。由于Hsfl和Hsf2具有不同的功能、调控机制和靶基因，但在功能上又存在一定的相互依赖性，因此我们有理由推测Hsf4与Hsfl和Hsf2在功能上存在重叠，但在维持细胞稳态方面也有其独特的作用。本资助申请中概述的研究旨在了解Hsf4在分子水平上的调控，并检查Hsf4不仅单独的功能，而且还与Hsfl和Hsf2在体内的功能协调。本建议的具体目标是：1。了解Hsf4在哺乳动物细胞中的调控分子机制。2. 探讨Hsf4在动物模型中的功能。3. 了解Hsf4剪接变异体在动物模型中的功能。

DESCRIPTION (provided by applicant): The functions of the mammalian heat shock transcription factors (Hsfs) are becoming increasingly clear with the recent generation of mice lacking the hsfl or hsf2. The results generated from analyses of these animal models are striking and indicative of the role of Hsfs in apoptosis, differentiation and development as well as maintenance of tissue homeostasis. To understand the functions of Hsfs in vivo, we have generated hsfl and hsf2 knockout mice and are now working to create mice that do not express hsf4. Disruption of hsfl illuminates its importance for regulation of apoptosis and control of thermotolerance and female sterility. In contrast, the hsf2 knockout mouse exhibits defects in development of the central nervous system and reduction in spermatogenesis. We further show evidence that deletion of both hsfl and hsf2 leads to synergistic effects and defects that are more severe than those manifested in individual hsf-deficient mice. These defects are associated with brain and behavioral abnormalities, and complete disruption of spermatogenesis and male sterility, as well as others. Compared to Hsfl and Hsf2, relatively little is known about the only remaining member of the mammalian Hsf family, Hsf4. Several features distinguish Hsf4 from other Hsfs. It is expressed as two alternatively spliced variants with one form being a transcriptional activator and the other a transcriptional repressor and these two variants are differentially expressed in different tissues. We show that Hsf4 is phosphorylated and a novel phosphatase (named DSPH4) containing signature motifs of the dual specificity tyrosine/serine/threonine phosphatases has been identified that binds to Hsf4 and modulates its phosphorylation status, DNA binding ability and nuclear localization. This represents a possible mechanism for the regulation of Hsf4 activity by extracellular signals. Because Hsfl and Hsf2 possess distinct functions, regulatory mechanisms, and target genes, but show some functional interdependency, it is reasonable to postulate that Hsf4 will also have some overlapping function with Hsfl and Hsf2, but also its own unique roles in maintaining cellular homeostasis. The studies outlined in this grant application are directed to understand the regulation of Hsf4 at the molecular level and to examine the function of Hsf4 not only alone, but also in coordination with Hsfl and Hsf2 functions in vivo. The Specific Aims of this proposal are: 1. To understand the molecular mechanisms of Hsf4 regulation in mammalian cells. 2. To investigate the function of Hsf4 in animal models. 3. To understand the function of Hsf4 splice variants in animal models.