Mechanism of Action of the HRPT2 Tumor Suppressor Gene Product Parafibromin

目前工作的目的是了解副纤维蛋白的调节，其生理靶点，以及其功能丧失导致肿瘤转化的机制(S)。为此，我们首先试图鉴定和表征昆虫和哺乳动物之间进化上保守的副纤维蛋白的功能。人副纤维蛋白通过人PAF1复合体与RNA聚合酶II相互作用，PAF1复合体的其他蛋白质成分包括人Paf1、CTR9、Leo1和WD40-重复蛋白Ski8。PAF1复合体的组成在进化上在果蝇中高度保守，副纤维蛋白与其在果蝇中的同源基因Hyrax(Hyx)有57%的氨基酸同源性和71%的相似性。如此高度的同源性表明该蛋白可能在不同物种中具有保守的功能作用。我们实验室目前的工作是使用黑腹果蝇和培养细胞，如人Hela和HEK-293细胞作为模型系统来研究这种共享的功能。其中一项研究使用了昆虫模型系统，在该系统中，果蝇Hyx(Parfiminin)是通过亚型等位基因表达的。在这个模型系统中，杂合子和纯合子都有表型。另一项研究研究哺乳动物副纤维蛋白的过度表达、突变或敲除(通过RNA干扰)对细胞增殖、细胞存活和Paf1复合体的核定位的影响。

The purpose of the current work is to understand the regulation of parafibromin, its physiologic targets, and the mechanism(s) by which its loss of function can lead to neoplastic transformation. To this end we are first trying to identify and characterize the functions parafibromin that are evolutionarily conserved between insects and mammals. Human parafibromin interacts with RNA polymerase II via a human PAF1 complex, whose other protein components include human Paf1, CTR9, Leo1, and the WD40-repeat protein Ski8. The components of the PAF1 complex are highly evolutionarily conserved in Drosophila and parafibromin shares 57% amino acid identity and 71% similarity with Hyrax (Hyx), its ortholog in the fly. Such a high degree of homology suggests a possible conserved functional role of the protein across species. Current work in our laboratory examines such shared functions using Drosophila melanogaster and cultured cells, such as human Hela and HEK-293 cells, as model systems. One line of research uses an insect model system in which Drosophila Hyx (parafibromin) is expressed from a hypomorphic allele. In this model system both hetero- and homozygotes have phenotypes. The other line of research studies the effect of mammalian parafibromin overexpression, mutation or knockdown (by RNA interference) on cell proliferation, cell survival, and nuclear localization of the Paf1 complex.