FUNCTION OF AN INTERFERON INDUCED UBIQUITIN HOMOLOG

描述（改编自申请人摘要）：干扰素诱导广泛的 多效性作用，包括生长抑制、抗肿瘤活性， 造血调节、细胞/体液免疫应答的控制，以及 抗病毒和寄生虫感染的活性， 这些细胞因子作为潜在的治疗剂。ISG 15的引入 ISG 15是最早的一个产生17.1 kDa多肽的基因， 对1型干扰素的反应。ISG 15（以前称为UCRP，泛素） 交叉反应蛋白）是最近发现的一类 泛素样蛋白似乎调节细胞功能，而不是 靶向易感蛋白质以供26 S蛋白酶体降解。在 与其他泛素样蛋白相比，ISG 15不存在于较低的细胞中。 真核生物，因此代表了相对较新的进化分歧。的 ISG 15的生物学效应是通过其共价连接到 小群体的细胞靶点，不同于那些被 其他泛素样蛋白。双混合屏幕最近确定了一个 一类高度保守的晚期干扰素诱导蛋白 1-8家庭。约14 kDa的多肽具有显著但神秘的 与泛素缀合的保守催化结构域的序列相似性 酶（Ubc）。本提案包括三个具体目标。具体目标 1将检验1-8种亚型代表ISG 15特异性的假设 通过体外测定和稳定的细胞转染， 多肽的活性和显性突变形式。其他研究将 专注于不同亚型之间的功能差异， 潜在的底物特异性和细胞定位。具体目标2 将重点关注9-27/Leu 13亚型及其在转导中的作用， 抗增殖和同型粘附信号。其他研究将绘制 9-27与普遍存在的四跨膜蛋白之间的蛋白质-蛋白质相互作用基序 CD 81及其与CD 19-CD 21的功能相互作用。第3章将 利用蛋白质组学和质谱蛋白质的最新进展 指纹识别，以确定目标群体的时间依赖性变化， 静止状态和干扰素诱导状态下的ISG 15缀合。这些研究 ISG 15缀合物和酶学的首次协同功能调查 这种修改。

DESCRIPTION (adapted from applicant's abstract): Interferons induce broad pleiotropic effects including growth inhibition, antitumor activity, hematopoietic regulation, control of cellular/humoral immune responses, and activity against viral and parasitic infection, accounting for interest in these cytokines as potential therapeutic agents. The induction of the ISG15 gene to generate the 17.1 kDa polypeptide ISG15 is one of the earliest responses to Type 1 interferons. ISG15 (formerly termed UCRP, the Ubiquitin Cross Reactive Protein) is the archetype of a recently discovered class of ubiquitin-like proteins that appear to regulate cellular function rather than to target susceptible proteins for degradation by the 26S proteasome. In contrast to the other ubiquitin-like proteins, ISG15 is not present in lower eukaryotes and thus represents a relatively recent evolutionary divergence. The biological effects of ISG15 are exerted through its covalent ligation to a small population of cellular targets that is distinct from those targeted by other ubiquitin-like proteins. Two-hybrid screens have recently identified a small class of highly conserved late interferon-induced proteins collectively termed the 1-8 family. The ca 14 kDa polypeptides bear remarkable yet cryptic sequence similarity to the conserved catalytic domain of ubiquitin conjugating enzymes (Ubc). The present proposal comprises three specific aims. Specific Aim 1 will test the hypothesis that 1-8 isoforms represent ISG15-specific conjugating enzymes through in vitro assays and stable cell transfections of active and dominant mutant forms of the polypeptides. Other studies will concentrate on functional differences among the different isoforms with respect to potential substrate specificity and cellular localization. Specific Aim 2 will focus on the 9-27/Leu13 isoform and its role in transducing antiproliferative and homotypic adhesion signals. Other studies will map protein-protein interaction motifs between 9-27 and the ubiquitous tetraspanin CD81 and their functional interactions with CD19-CD21. Specific Aim 3 will exploit recent advances in proteomics and mass spectroscopic protein fingerprinting to identify time-dependent changes in populations of targets for ISG15 conjugation in quiescent and interferon induced states. These studies are the first concerted functional survey of ISG15 conjugation and the enzymology of this modification.