Analysis of the non-endosomal function of ESCRT-III proteins

内化的细胞表面蛋白在进入溶酶体/液泡进行降解的过程中要经过几个内体隔室。胞内转运是由一系列复杂的蛋白质功能介导的，其中许多功能已通过遗传筛选在酿酒酵母中得到鉴定。一些蛋白质被分成复合体(ESCRT复合体)，它们在晚期内小体水平上连续发挥作用。其中一个复合体，ESCRT-III复合体，是由一系列小卷曲形成蛋白组成的。虽然所有这些蛋白质都在内吞途径的共同步骤中发挥作用，但相应的突变体表现出不同的表型。遗传分析表明，这些蛋白质具有独立于其内体功能的额外功能。在这个项目中，我们将研究ESCRT-III蛋白的这种非内体功能。我们将关注这个蛋白质家族中的一个成员，Snf7蛋白。除了其内体作用外，Snf7还影响核内基因的表达。我们将研究Snf7如何干扰细胞核中的基因表达。

Internalized cell surface proteins pass through several endosomal compartments on their way to the lysosome/vacuole for degradation. Endocytic transport is mediated by a complex array of protein functions, many of which have been identified through genetic screens in the yeast Saccharomyces cerevisiae. Some of the proteins have been grouped into complexes ( ESCRT complexes ) that function consecutively at the level of late endosomes. One of these complexes, the ESCRT-III complex, is made up of a family of small coiled-coil forming proteins. Although all of these proteins function at a common step in the endocytic pathway, the corresponding mutants show distinct phenotypes. Genetic analyses suggest that these proteins have additional functions that are separate from their endosomal function. In this project, we will examine this non-endosomal function of the ESCRT-III proteins. We will focus on one member of this protein family, the Snf7 protein. In addition to its endosomal role, Snf7 affects the expression of genes in the nucleus. We will investigate how Snf7 interferes with gene expression in the nucleus.