FUNCTION OF INTERFERON INDUCED PROTEIN KINASE PKR (DAI)

蛋白激酶在高等生物的细胞调控回路中起着关键作用。RNA依赖的蛋白激酶PKR，以前被称为DAI，是翻译控制机制和干扰素诱导的抗病毒反应的关键元件。最近，它参与了更多的途径：包括凋亡、分化、生长控制、信号转导、应激和转化。细胞和病毒成分作为激活剂、抑制物和底物与PKR相互作用，强调其在细胞调控过程中的关键地位。这项研究的目的是为了了解PKR的调节以及它控制其他细胞蛋白活性的方式。最近发现PKR与两种重要的核蛋白形成络合物并使其磷酸化。一种是RNA解旋酶A(RHA)，它是一种重要的DNA/RNA解旋酶，也是一种转录辅助激活因子。第二种是被称为NF90/NF45的活化T细胞核因子(NFAT)：这是一种序列特异性DNA结合蛋白，可能受细胞周期调节。特别是，该项目旨在阐明激活PKR蛋白激酶功能的细胞大分子的性质，以及在这种激活过程中所需的酶的变化。将定义涉及PKR、RHA和NF90/NF45的新的蛋白质-蛋白质相互作用，并探讨它们对病毒感染、基因表达和细胞转化的意义。这些蛋白质还与高度结构的RNA分子相互作用，包括dsRNA和腺病毒VA RNAs，这表明它们参与了RNA调节的途径。了解这些细胞成分的活动、控制和相互作用可能会导致癌症和病毒性疾病的干预策略。

Protein kinases play critical roles in the cellular regulatory circuits of higher organisms. The RNA-dependent protein kinase PKR, formerly called DAI, is well established as a key element of translational control mechanisms and of the interferon-induced antiviral response. More recently, its involvement in additional pathways has become apparent: these include apoptosis, differentiation, growth control, signal transduction, stress, and transformation. Cellular and viral components interact with PKR as activators, inhibitors, and substrates, emphasizing its pivotal position in cellular regulatory processes. The objectives of the research proposed here are to understand the regulation of PKR and the means by which it controls the activity of other cell proteins. PKR has recently been found to complex with and phosphorylate two important nuclear proteins. One is RNA helicase A (RHA), an essential DNA/RNA helicase which also serves as a transcription coactivator. The second is a nuclear factor of activated T cells (NFAT) known as NF90/NF45: this is a sequence-specific DNA binding protein which may be cell cycle-regulated. In particular, the project aims to elucidate the nature of the cellular macromolecules that activate PKR's protein kinase function, and the changes in the enzyme that are entailed in this activation. The novel protein-protein interactions involving PKR, RHA and NF90/NF45 will be defined and their implications for virus infection, gene expression, and cellular transformation will be explored. These proteins also interact with highly structured RNA molecules, including dsRNA and the adenovirus VA RNAs, suggestive of participation in RNA-regulated pathways. Understanding the activities, controls, and interactions of these cellular components may lead to strategies for intervention in cancer and viral disease.