Mechanism of Action of the HRPT2 Tumor Suppressor Gene Product Parafibromin

当前工作的目的是了解副纤白蛋白的调控，其生理靶点，以及其功能丧失导致肿瘤转化的机制。为此，我们首先试图确定和描述在昆虫和哺乳动物之间进化保守的副纤白蛋白的功能。人副纤白蛋白通过人PAF1复合物与RNA聚合酶II相互作用，该复合物的其他蛋白质成分包括人PAF1、CTR9、Leo1和WD40-repeat蛋白Ski8。PAF1复合体的组成部分在果蝇中具有高度的进化保守性，而parafibromin与其在果蝇中的同源物Hyrax （Hyx）具有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在物种间可能具有保守的功能作用。我们实验室目前的工作是利用黑腹果蝇和培养细胞（如人类Hela和HEK-293细胞）作为模型系统来研究这些共享功能。其中一项研究使用了一种昆虫模型系统，其中果蝇Hyx（副纤维蛋白）是由一个半胚等位基因表达的。在这个模型系统中，杂合子和纯合子都有表型。另一个研究方向是研究哺乳动物对异丙酚蛋白的过表达、突变或敲低（通过RNA干扰）对细胞增殖、细胞存活以及其他在细胞生长和增殖中重要基因的表达的影响。我们也在体外研究了CDC73/HRPT2杂合患者的白细胞。

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 expression of other genes important in cell growth and proliferation. White blood cells from patients heterozygous for CDC73/HRPT2 are also studied in vitro.