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Yanping Chen, Yingjun Chi, Qingchang Meng, Xiaolin Wang, Deyue Yu
In plants, various proteins are regulated by the ubiquitin-mediated system in response to different environmental stresses, such as drought, cold and heat. The Skp1-Cullin-F-box (SCF) complex, one of the multisubunit E3 ligases, has been shown to be involved in abiotic response pathways. In this study, Glycine max SKP1-like 1 (GmSK1), which had the typical characteristics of an SKP1 protein, with an alpha/beta structure, targeted to the cytoplasm and nucleus, was isolated from soybean [Glycine max (L.)]. GmSK1 was constitutively expressed in all the tested tissues, especially in the roots...
March 7, 2018: Plant Physiology and Biochemistry: PPB
Xing Liu, Justin M Reitsma, Jennifer L Mamrosh, Yaru Zhang, Ronny Straube, Raymond J Deshaies
Skp1⋅Cul1⋅F-box (SCF) ubiquitin ligase assembly is regulated by the interplay of substrate binding, reversible Nedd8 conjugation on Cul1, and the F-box protein (FBP) exchange factors Cand1 and Cand2. Detailed investigations into SCF assembly and function in reconstituted systems and Cand1/2 knockout cells informed the development of a mathematical model for how dynamical assembly of SCF complexes is controlled and how this cycle is coupled to degradation of an SCF substrate. Simulations predicted an unanticipated hypersensitivity of Cand1/2-deficient cells to FBP expression levels, which was experimentally validated...
March 1, 2018: Molecular Cell
Kouhei Shimizu, Naoe Taira Nihira, Hiroyuki Inuzuka, Wenyi Wei
FBW7 is one of the most well characterized F-box proteins that serve as substrate recognition subunits of SCF (Skp1-Cullin 1-F-box proteins) E3 ubiquitin ligase complexes. SCFFBW7 plays key roles in regulating cell cycle progression, differentiation, and stem cell maintenance largely through targeting a broad range of oncogenic substrates for proteasome-dependent degradation. The identification of an increasing number of FBW7 substrates for ubiquitination, and intensive in vitro and in vivo studies have revealed a network of signaling components controlled by FBW7 that contributes to metabolic regulation as well as its tumor suppressor role...
February 20, 2018: Cellular Signalling
Hongchao He, Jun Dai, Zhaoping Xu, Wei He, Xiaojing Wang, Yu Zhu, Haofei Wang
F-box and WD repeat domain containing 7 (Fbxw7) is an F-box protein that belongs to the SKP1-CUL1-F-box protein E3 ligase complex and is responsible for transferring the ubiquitin molecule to the substrate, which results in its recognition and subsequent degradation by proteasomes. Furthermore, it can identify a network of signaling proteins that function in cell growth, diversion and apoptosis. In the present study, Fbxw7 was downregulated in renal cell carcinoma (RCC) tissues compared with the adjacent non-tumor tissues and its expression was significantly associated with the tumor-node-metastasis stage, lymph node metastasis and distant metastasis in patients with RCC...
March 2018: Oncology Letters
Christian Arquint, Fabien Cubizolles, Agathe Morand, Alexander Schmidt, Erich A Nigg
Deregulation of centriole duplication has been implicated in cancer and primary microcephaly. Accordingly, it is important to understand how key centriole duplication factors are regulated. E3 ubiquitin ligases have been implicated in controlling the levels of several duplication factors, including PLK4, STIL and SAS-6, but the precise mechanisms ensuring centriole homeostasis remain to be fully understood. Here, we have combined proteomics approaches with the use of MLN4924, a generic inhibitor of SCF E3 ubiquitin ligases, to monitor changes in the cellular abundance of centriole duplication factors...
February 2018: Open Biology
Ruikang Liu, Bernard Moss
Type I interferons (IFNs) induce expression of more than 300 cellular genes that provide protection against viruses and other pathogens. For survival, viruses evolved defenses to prevent the IFN response or counteract the IFN-induced antiviral state. However, because viruses and cells co-evolved, the dynamic relationship between virus and host is difficult to discern. In the present study, we demonstrated that vaccinia virus with a large deletion near the left end of the genome had a diminished ability to replicate in cells that had been pre-treated with IFNβ, suggesting that one or more of the missing 17 open reading frames (ORFs) encodes an antagonist of the IFN-induced antiviral state...
February 14, 2018: Journal of Virology
Tsuneo Ikenoue, Yumi Terakado, Chi Zhu, Xun Liu, Tomoyuki Ohsugi, Daisuke Matsubara, Tomoki Fujii, Shigeru Kakuta, Sachiko Kubo, Takuma Shibata, Kiyoshi Yamaguchi, Yoichiro Iwakura, Yoichi Furukawa
F-box and WD40 domain protein 7 (FBXW7) is a component of the SKP1-CUL1-F-box protein (SCF) complex that mediates the ubiquitination of diverse oncogenic target proteins. The exploration of FBXW7 mutations in human primary cancer has revealed three mutation hotspots at conserved arginine residues (Arg465 , Arg479 , and Arg505 ) in the WD40 domain, which are critical for substrate recognition. To study the function of human FBXW7R465C , the most frequent mutation in human malignancies, we generated a novel conditional knockin mouse line of murine Fbxw7R468C corresponding to human FBXW7R465C ...
January 31, 2018: Scientific Reports
Cui Qiu, Yuan-Yuan Yi, Rafael Lucena, Meng-Juan Wu, Jia-Hao Sun, Xi Wang, Quan-Wen Jin, Yamei Wang
The key kinase Cdk1 (Cdc2) promotes irreversible mitotic entry mainly by activating the phosphatase Cdc25 while suppressing the tyrosine kinase Wee1. Wee1 needs to be down-regulated at the onset of mitosis to ensure rapid activation of Cdk1. In human somatic cells, one mechanism of suppressing Wee1 activity is mediated by ubiquitylation-dependent proteolysis through the Skp1/Cul1/F-box protein (SCF) ubiquitin E3 ligase complex. This mechanism is believed to be conserved from yeasts to humans. So far, the best characterized human F-box proteins involved in recognition of Wee1 are β-TrCP and Tome-1...
December 19, 2017: Journal of Cell Science
Ella Fung, Carmen Richter, Hong-Bin Yang, Isabell Schäffer, Roman Fischer, Benedikt M Kessler, Florian Bassermann, Vincenzo D'Angiolella
Aberrant centrosome organisation with ensuing alterations of microtubule nucleation capacity enables tumour cells to proliferate and invade despite increased genomic instability. CEP192 is a key factor in the initiation process of centrosome duplication and in the control of centrosome microtubule nucleation. However, regulatory means of CEP192 have remained unknown. Here, we report that FBXL13, a binding determinant of SCF (SKP1-CUL1-F-box)-family E3 ubiquitin ligases, is enriched at centrosomes and interacts with the centrosomal proteins Centrin-2, Centrin-3, CEP152 and CEP192...
January 18, 2018: EMBO Reports
Wei-Li Guo, Bi-Hua Chen, Xue-Jin Chen, Yan-Yan Guo, He-Lian Yang, Xin-Zheng Li, Guang-Yin Wang
Cucurbit powdery mildew (PM) is one of the most severe fungal diseases, but the molecular mechanisms underlying PM resistance remain largely unknown, especially in pumpkin (Cucurbita moschata Duch.). The goal of this study was to identify gene expression differences in PM-treated plants (harvested at 24 h and 48 h after inoculation) and untreated (control) plants of inbred line "112-2" using RNA sequencing (RNA-Seq). The inbred line "112-2" has been purified over 8 consecutive generations of self-pollination and shows high resistance to PM...
2018: PloS One
Jia Shen, Charles Spruck
Epigenetic abnormalities are now realized as important as genetic alterations in contributing to the initiation and progression of cancer. Recent advancements in the cancer epigenetics field have identified extensive alterations of the epigenetic network in human cancers, including histone modifications and DNA methylation. F-box proteins, the substrate receptors of SCF (SKP1-Cullin1-F-box protein) E3 ubiquitin ligases, can directly and indirectly affect the balance of epigenetic regulation. In this brief review, we discuss our current understanding of F-box proteins in cellular epigenetic regulation and how dysregulation of these processes contribute to cancer development...
December 15, 2017: Oncotarget
Eva Juengel, Ramin Najafi, Jochen Rutz, Sebastian Maxeiner, Jasmina Makarevic, Frederik Roos, Igor Tsaur, Axel Haferkamp, Roman A Blaheta
Introduction: Although the mechanistic target of rapamycin (mTOR) might be a promising molecular target to treat advanced bladder cancer, resistance develops under chronic exposure to an mTOR inhibitor (everolimus, temsirolimus). Based on earlier studies, we proposed that histone deacetylase (HDAC) blockade might circumvent resistance and investigated whether HDAC inhibition has an impact on growth of bladder cancer cells with acquired resistance towards temsirolimus. Results: The HDAC inhibitor valproic acid (VPA) significantly inhibited growth, proliferation and caused G0/G1 phase arrest in RT112res and UMUC-3res...
December 15, 2017: Oncotarget
Yunfeng Li, Kai Jin, Eric Bunker, Xiaojuan Zhang, Xuemei Luo, Xuedong Liu, Bing Hao
Ubiquitin-dependent proteolysis of cyclin D1 is associated with normal and tumor cell proliferation and survival. The SCFFBXO31 (Skp1-Cul1-Rbx1-FBXO31) ubiquitin ligase complex mediates genotoxic stress-induced cyclin D1 degradation. Previous studies have suggested that cyclin D1 levels are maintained at steady state by phosphorylation-dependent nuclear export and subsequent proteolysis in the cytoplasm. Here we present the crystal structures of the Skp1-FBXO31 complex alone and bound to a phosphorylated cyclin D1 C-terminal peptide...
December 26, 2017: Proceedings of the National Academy of Sciences of the United States of America
Xianzhong Xu, Alexander Eletsky, M Osman Sheikh, James H Prestegard, Christopher M West
Cullin-Ring-Ligases mediate protein polyubiquitination, a signal for degradation in the 26S-proteasome. The CRL1 class consists of Skp1/cullin-1/F-box protein/Rbx1 (SCF) complexes that cyclically associate with ubiquitin-E2 to build the polyubiquitin chain. Within the SCF complex, the 162-amino acid DdSkp1 from Dictyostelium bridges cullin-1 with an F-box protein (FBP), the specificity factor for substrate selection. The hydroxylation-dependent glycosylation of Pro143 of DdSkp1 by a pentasaccharide forms the basis of a novel O2-sensing mechanism in the social amoeba Dictyostelium and other protists...
December 18, 2017: Biochemistry
Vera Leber, Andrea Nans, Martin R Singleton
Eukaryotic chromosomes contain a specialised region known as the centromere, which forms the platform for kinetochore assembly and microtubule attachment. The centromere is distinguished by the presence of nucleosomes containing the histone H3 variant, CENP-A. In budding yeast, centromere establishment begins with the recognition of a specific DNA sequence by the CBF3 complex. This in turn facilitates CENP-ACse4 nucleosome deposition and kinetochore assembly. Here, we describe a 3.6 Å single-particle cryo-EM reconstruction of the core CBF3 complex, incorporating the sequence-specific DNA-binding protein Cep3 together with regulatory subunits Ctf13 and Skp1...
January 17, 2018: EMBO Journal
Linhan Sun, Teh-Hui Kao
Function of Petunia PiSSK1. Self-incompatibility (SI), an inbreeding-preventing mechanism, is regulated in Petunia inflata by the polymorphic S-locus, which houses multiple pollen-specific S-locus F-box (SLF) genes and a single pistil-specific S-RNase gene. S2 -haplotype and S3 -haplotype possess the same 17 polymorphic SLF genes (named SLF1 to SLF17), and each SLF protein produced in pollen is assembled into an SCF (Skp1-Cullin1-F-box) E3 ubiquitin ligase complex. A complete suite of SLF proteins is thought to collectively interact with all non-self S-RNases to mediate their ubiquitination and degradation by the 26S proteasome, allowing cross-compatible pollination...
November 30, 2017: Plant Reproduction
Luigi Alfano, Antonella Caporaso, Angela Altieri, Caterina Costa, Iris M Forte, Carmelina A Iannuzzi, Daniela Barone, Luca Esposito, Antonio Giordano, Francesca Pentimalli
NONO is an RNA-binding protein involved in transcription, mRNA splicing, DNA repair and checkpoint activation in response to UV radiation. NONO expression has been found altered in several tumour types, including prostate, colon, breast, melanoma and in papillary renal carcinoma, in which an X chromosome inversion generates a NONO-TFE3 fusion protein. Upon such rearrangement, NONO loses its C-terminal domain. Through bioinformatics analysis, we identified a putative degron motif, known to be recognized by the Skp1-Cul1-F-box-protein (SCF) complex...
November 18, 2017: Journal of Cellular Physiology
Shuo Qie, Mrinmoyee Majumder, Katarzyna Mackiewicz, Breege V Howley, Yuri K Peterson, Philip H Howe, Viswanathan Palanisamy, J Alan Diehl
The Fbxo4 tumour suppressor is a component of an Skp1-Cul1-F-box E3 ligase for which two substrates are known. Here we show purification of SCF(Fbxo4) complexes results in the identification of fragile X protein family (FMRP, Fxr1 and Fxr2) as binding partners. Biochemical and functional analyses reveal that Fxr1 is a direct substrate of SCF(Fbxo4). Consistent with a substrate relationship, Fxr1 is overexpressed in Fbxo4 knockout cells, tissues and in human cancer cells, harbouring inactivating Fbxo4 mutations...
November 16, 2017: Nature Communications
Shuiyan Zou, Cunying Ma, Fenghua Yang, Xia Xu, Jihui Jia, Zhifang Liu
The F-box protein FBXO31, a component of the Skp1/Cul1/F-box (SCF) E3 ubiquitin ligase complex, plays an important regulatory role in neuronal development, stress response, and tumorigenesis. Our recent report indicates that FBXO31 functions as a tumor suppressor in gastric cancer, and the loss of FBXO31 protein is associated with a higher malignant phenotype and poorer prognosis. However, little is known about the underlying mechanism. In this study, FBXO31 inhibits gastric cancer progression by suppressing the epithelial-mesenchymal transition (EMT)...
February 2018: Molecular Cancer Research: MCR
Justin M Reitsma, Xing Liu, Kurt M Reichermeier, Annie Moradian, Michael J Sweredoski, Sonja Hess, Raymond J Deshaies
SCF (Skp1-Cullin-F-box) ubiquitin ligases comprise several dozen modular enzymes that have diverse roles in biological regulation. SCF enzymes share a common catalytic core containing Cul1⋅Rbx1, which is directed toward different substrates by a variable substrate receptor (SR) module comprising 1 of 69 F-box proteins bound to Skp1. Despite the broad cellular impact of SCF enzymes, important questions remain about the architecture and regulation of the SCF repertoire, including whether SRs compete for Cul1 and, if so, how this competition is managed...
November 30, 2017: Cell
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