ABSTRACT
Nuclear pore complexes (NPCs) are important for cellular functions beyond nucleocytoplasmic trafficking, including genome organization and gene expression. This multi-faceted nature and the slow turnover of NPC components complicates investigations of how individual nucleoporins act in these diverse processes. To address this question, we apply an Auxin-Induced Degron (AID) system to distinguish roles of basket nucleoporins NUP153, NUP50 and TPR. Acute depletion of TPR causes rapid and pronounced changes in transcriptomic profiles. These changes are dissimilar to shifts observed after loss of NUP153 or NUP50, but closely related to changes caused by depletion of mRNA export receptor NXF1 or the GANP subunit of the TRanscription-EXport-2 (TREX-2) mRNA export complex. Moreover, TPR depletion disrupts association of TREX-2 subunits (GANP, PCID2, ENY2) to NPCs and results in abnormal RNA transcription and export. Our findings demonstrate a unique and pivotal role of TPR in gene expression through TREX-2- and/or NXF1-dependent mRNA turnover.
Subject(s)
Exodeoxyribonucleases/metabolism , Nuclear Pore Complex Proteins/metabolism , Nuclear Pore/metabolism , Phosphoproteins/metabolism , RNA, Messenger/metabolism , Cell Line , Gene Expression Regulation , Humans , Indoleacetic Acids/metabolism , Nuclear Proteins , Nucleocytoplasmic Transport Proteins , Protein Transport , RNA-Binding Proteins , Transcriptome , Zinc FingersABSTRACT
The Ran GTPase plays critical roles in multiple cellular processes including interphase nucleocytoplasmic transport and mitotic spindle assembly. During mitosis in mammalian cells, GTP-bound Ran (Ran-GTP) is concentrated near mitotic chromatin while GDP-bound Ran (Ran-GDP) is more abundant distal to chromosomes. This pattern spatially controls spindle formation because Ran-GTP locally releases spindle assembly factors (SAFs), such as Hepatoma Up-Regulated Protein (HURP), from inhibitory interactions near chromosomes. Regulator of Chromatin Condensation 1 (RCC1) is Ran's chromatin-bound exchange factor, and RanBP1 is a conserved Ran-GTP-binding protein that has been implicated as a mitotic regulator of RCC1 in embryonic systems. Here, we show that RanBP1 controls mitotic RCC1 dynamics in human somatic tissue culture cells. In addition, we observed the re-localization of HURP in metaphase cells after RanBP1 degradation, consistent with the idea that altered RCC1 dynamics functionally modulate SAF activities. Together, our findings reveal an important mitotic role for RanBP1 in human somatic cells, controlling the spatial distribution and magnitude of mitotic Ran-GTP production and thereby ensuring the accurate execution of Ran-dependent mitotic events. ABBREVIATIONS: AID: Auxin-induced degron; FLIP: Fluorescence loss in photobleaching; FRAP: Fluorescence recovery after photobleaching; GDP: guanosine diphosphate; GTP: guanosine triphosphate; HURP: Hepatoma Up-Regulated Protein; NE: nuclear envelope; NEBD: Nuclear Envelope Breakdown; RanBP1: Ran-binding protein 1; RanGAP1: Ran GTPase-Activating Protein 1; RCC1: Regulator of Chromatin Condensation 1; RRR complex: RCC1/Ran/RanBP1 heterotrimeric complex; SAF: Spindle Assembly Factor; TIR1: Transport Inhibitor Response 1 protein; XEE: Xenopus egg extract.
Subject(s)
Cell Cycle Proteins/metabolism , Guanine Nucleotide Exchange Factors/metabolism , Mammals/metabolism , Mitosis , Nuclear Proteins/metabolism , Signal Transduction , ran GTP-Binding Protein/metabolism , Anaphase/drug effects , Animals , Cell Line, Tumor , Cell Proliferation/drug effects , Chromatin/metabolism , Chromosomes, Mammalian/metabolism , Indoleacetic Acids/pharmacology , Metaphase/drug effects , Mitosis/drug effects , Models, Biological , Neoplasm Proteins/metabolism , Protein Binding/drug effects , Proteolysis/drug effects , Signal Transduction/drug effects , Spindle Apparatus/drug effects , Spindle Apparatus/metabolism , Xenopus laevisABSTRACT
Despite being a potent hypolipidemic drug, atorvastatin (AS) possesses certain adverse effects. Using AS and an herbal formula (Danshen and Gegen, DG) in combination may achieve potentiated hypolipidemic effects and also reduce its adverse effects. Hence, this study aimed to investigate the efficacy and safety of an AS and DG combination on high-fat diet-induced hyperlipidemia. Treatment outcomes were assessed by measuring parameters including body weight, adipose tissue, liver, total cholesterol, triglyceride, and low-density and high-density lipoprotein cholesterol. Measurements of adverse effects were achieved by determining aspartate aminotransferase (AST), alanine transaminase (ALT), and creatine kinase (CK). Danshen and Gegen, as well as AS alone, reduced body weight, adipose tissue, liver weight, liver fat vacuoles, total liver lipids, total cholesterol, triglyceride, low-density lipoprotein cholesterol, and high-density lipoprotein cholesterol in high-fat diet-fed mice but increased AST, ALT, and CK. A combination of AS and DG was able to enhance reduced effects on the aforementioned parameters in relation to hyperlipidemia over AS or DG alone. It also reduced the elevation of AST, ALT, and CK induced than by AS or DG alone. Results demonstrated that an AS and DG combination resulted in stronger hypolipidemic effects than with AS or DG alone. Additionally, DG might attenuate adverse effects of AS on the liver and skeletal muscle. Copyright © 2017 John Wiley & Sons, Ltd.
