Genetic Analysis of Pathways Regulated by the von Hippel-Lindau Tumor Suppressor in Caenorhabditis elegans

The von Hippel-Lindau (VHL) tumor suppressor functions as a ubiquitin ligase that mediates proteolytic inactivation of hydroxylated α subunits of hypoxia-inducible factor (HIF). Although studies of VHL-defective renal carcinoma cells suggest the existence of other VHL tumor suppressor pathways, dysregulation of the HIF transcriptional cascade has extensive effects that make it difficult to distinguish whether, and to what extent, observed abnormalities in these cells represent effects on pathways that are distinct from HIF. Here, we report on a genetic analysis of HIF-dependent and -independent effects of VHL inactivation by studying gene expression patterns in Caenorhabditis elegans. We show tight conservation of the HIF-1/VHL-1/EGL-9 hydroxylase pathway. However, persisting differential gene expression in hif-1 versus hif-1; vhl-1 double mutant worms clearly distinguished HIF-1–independent effects of VHL-1 inactivation. Genomic clustering, predicted functional similarities, and a common pattern of dysregulation in both vhl-1 worms and a set of mutants (dpy-18, let-268, gon-1, mig-17, and unc-6), with different defects in extracellular matrix formation, suggest that dysregulation of these genes reflects a discrete HIF-1–independent function of VHL-1 that is connected with extracellular matrix function.

希佩尔-林道肿瘤抑制因子（von Hippel-Lindau, VHL）作为一种泛素连接酶，可介导缺氧诱导因子（hypoxia-inducible factor, HIF）羟化α亚基的蛋白水解失活。尽管针对VHL缺陷型肾癌细胞的研究提示存在其他VHL肿瘤抑制通路，但HIF转录级联反应的失调会产生广泛影响，使得难以分辨这些细胞中观察到的异常究竟在多大程度上代表了独立于HIF的通路效应。本研究通过分析秀丽隐杆线虫（Caenorhabditis elegans）的基因表达模式，对VHL失活的HIF依赖与非依赖效应开展了遗传学分析。研究证实了HIF-1/VHL-1/EGL-9羟化酶通路的高度保守性；然而，hif-1突变体与hif-1; vhl-1双突变体线虫之间持续存在的差异基因表达，清晰区分了VHL-1失活的HIF-1非依赖效应。对vhl-1突变体线虫及一组细胞外基质形成存在不同缺陷的突变体（dpy-18、let-268、gon-1、mig-17及unc-6）的基因组聚类分析、预测功能相似性分析，以及二者共有的失调表达模式表明，这些基因的失调反映了VHL-1一项独立于HIF-1的独特功能，该功能与细胞外基质功能相关。