A C-terminal targeting signal controls differential compartmentalisation of Caenorhabditis elegans host cell factor (HCF) to the nucleus or mitochondria
A C-terminal targeting signal controls differential compartmentalisation of Caenorhabditis elegans host cell factor (HCF) to the nucleus or mitochondria
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DOI：
10.1078/0171-9335-00341
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发表时间：
2003-10-01
影响因子：
6.6
通讯作者：
O'Hare, P
中科院分区：
文献类型：
--
作者：
Izeta, A;Malcomber, S;O'Hare, P
HCF-1（宿主细胞因子1）是一种人类蛋白质，最初被鉴定为VP 16转录复合物的组分。一种相关的蛋白质HCF-2也存在于人类中，虽然至少HCF-1似乎是正常细胞生长所必需的，但目前关于这些蛋白质的确切细胞作用的信息很少。C.线虫含有一个与人HCF-2非常密切相关的HCF直向同源物（CeHCF）。为了有助于了解这些蛋白质的活性，我们在这里分析了CeHCF蛋白在活的转基因蠕虫和哺乳动物细胞中的亚细胞定位。我们构建了CeHCF的绿色荧光蛋白（GFP）融合体，并研究了热休克蛋白启动子控制下异位表达后的定位。CeHCF-GFP蛋白在发育的每个阶段和多种细胞类型的细胞核中积累。在幼虫和成虫阶段，核仁保留的核积累是明显的，但在发育早期，蛋白质在核质中弥散积累。令人惊讶的是，相同的蛋白质在稳定的HeLa细胞系的线粒体中积累，表明CeHCF在哺乳动物细胞中的差异定位。此外，当在瞬时转染中过表达时，CeHCF在细胞核和线粒体隔室中积累。我们已经将CeHCF的靶向决定簇细化到最末端C-末端的最后23个氨基酸，并表明它们含有参与核和线粒体靶向的叉指型氨基酸。这种新的靶向信号足以将HCF-2重定向到线粒体中。它也可以转移到一个不相关的蛋白质，导致其靶向线粒体和核隔室。
HCF-1 (host cell factor 1) is a human protein originally identified as a component of the VP16 transcription complex. A related protein HCF-2 is also present in humans and while at least HCF-1 appears to be required for normal cell growth there is currently little information on the precise cellular role(s) of these proteins. C. elegans contains a single HCF orthologue (CeHCF) which is very closely related to human HCF-2. To contribute to an understanding of the activities of these proteins here we analyse the subcellular localisation of the CeHCF protein in live transgenic worms and in mammalian cells. We constructed a green fluorescent protein (GFP) fusion of CeHCF and studied localisation after ectopic expression under the control of a heat shock protein promoter. The CeHCF-GFP protein accumulated in the cell nuclei at every stage of development and in a wide variety of cell types. Nuclear accumulation with nucleolar sparing was evident on the larvae and adult stages, but not earlier in development in which the protein accumulated diffusely in the nucleoplasm. Surprisingly the same protein accumulated in the mitochondria of a stable HeLa cell line, suggesting a differential localisation of CeHCF in mammalian cells. Furthermore, when overexpressed in transient transfection the CeHCF accumulated in both nuclear and mitochondrial compartments. We have refined the targeting determinants of CeHCF to the last 23 amino acids at the extreme C-terminus and show that they contain interdigitated amino acids involved in both nuclear and mitochondrial targeting. This novel targeting signal is sufficient to redirect HCF-2 into mitochondria. It can also be transferred to an unrelated protein, resulting in its targeting to both the mitochondrial and nuclear compartments.