1
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Zeng G, Zheng Y, Xiang Y, Liu R, Yang X, Lin Z. A novel protein purification scheme based on salt inducible self-assembling peptides. Microb Cell Fact 2023; 22:224. [PMID: 37899435 PMCID: PMC10614350 DOI: 10.1186/s12934-023-02229-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2023] [Accepted: 10/12/2023] [Indexed: 10/31/2023] Open
Abstract
BACKGROUND Protein purification remains a critical need for biosciences and biotechnology. It frequently requires multiple rounds of chromatographic steps that are expensive and time-consuming. Our lab previously reported a cleavable self-aggregating tag (cSAT) scheme for streamlined protein expression and purification. The tag consists of a self-assembling peptide (SAP) and a controllable self-cleaving intein. The SAP drives the target protein into an active aggregate, then by intein-mediated cleavage, the target protein is released. Here we report a novel cSAT scheme in which the self-assembling peptide is replaced with a salt inducible self-assembling peptide. This allows a target protein to be expressed first in the soluble form, and the addition of salt then drives the target protein into the aggregated form, followed by cleavage and release. RESULTS In this study, we used MpA (MKQLEDKIEELLSKAAMKQLEDKIEELLSK) as a second class of self-assembling peptide in the cSAT scheme. This scheme utilizes low salt concentration to keep the fusion protein soluble, while eliminating insoluble cellular matters by centrifugation. Salt then triggers MpA-mediated self-aggregation of the fusion, removing soluble background host cell proteins. Finally, intein-mediated cleavage releases the target protein into solution. As a proof-of-concept, we successfully purified four proteins and peptides (human growth hormone, 22.1 kDa; LCB3, 7.7 kDa; SpyCatcherΔN-ELP-SpyCatcherΔN, 26.2 kDa; and xylanase, 45.3 kDa) with yields ranging from 12 to 87 mg/L. This was comparable to the classical His-tag method both in yield and purity (72-97%), but without the His-tag. By using a further two-step column purification process that included ion-exchange chromatography and size-exclusion chromatography, the purity was increased to over 99%. CONCLUSION Our results demonstrate that a salt-inducible self-assembling peptide can serve as a controllable aggregating tag, which might be advantageous in applications where soluble expression of the target protein is preferred. This work also demonstrates the potential and advantages of utilizing salt inducible self-assembling peptides for protein separation.
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Affiliation(s)
- Guang Zeng
- School of Biology and Biological Engineering, South China University of Technology, 382 East Outer Loop Road, University Park, Guangzhou, 510006, China
| | - Yinzhen Zheng
- School of Biology and Biological Engineering, South China University of Technology, 382 East Outer Loop Road, University Park, Guangzhou, 510006, China
| | - Ya Xiang
- School of Biology and Biological Engineering, South China University of Technology, 382 East Outer Loop Road, University Park, Guangzhou, 510006, China
| | - Run Liu
- School of Biology and Biological Engineering, South China University of Technology, 382 East Outer Loop Road, University Park, Guangzhou, 510006, China
| | - Xiaofeng Yang
- School of Biology and Biological Engineering, South China University of Technology, 382 East Outer Loop Road, University Park, Guangzhou, 510006, China.
| | - Zhanglin Lin
- School of Biology and Biological Engineering, South China University of Technology, 382 East Outer Loop Road, University Park, Guangzhou, 510006, China.
- Shenzhen Institute of Synthetic Biology, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, China.
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2
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Li P, Zhen Y, Kim C, Liu Z, Hao J, Deng H, Deng H, Zhou M, Wang XD, Qin T, Yu Y. Nimbolide targets RNF114 to induce the trapping of PARP1 and synthetic lethality in BRCA-mutated cancer. SCIENCE ADVANCES 2023; 9:eadg7752. [PMID: 37878693 PMCID: PMC10599614 DOI: 10.1126/sciadv.adg7752] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/19/2023] [Accepted: 09/22/2023] [Indexed: 10/27/2023]
Abstract
Recent studies have pointed to PARP1 trapping as a key determinant of the anticancer effects of PARP1 inhibitors (PARPi). We identified RNF114, as a PARylation-dependent, E3 ubiquitin ligase involved in DNA damage response. Upon sensing genotoxicity, RNF114 was recruited, in a PAR-dependent manner, to DNA lesions, where it targeted PARP1 for degradation. The blockade of this pathway interfered with the removal of PARP1 from DNA lesions, leading to profound PARP1 trapping. We showed that a natural product, nimbolide, inhibited the E3 ligase activity of RNF114 and thus caused PARP1 trapping. However, unlike conventional PARPi, nimbolide treatment induced the trapping of both PARP1 and PARylation-dependent DNA repair factors. Nimbolide showed synthetic lethality with BRCA mutations, and it overcame intrinsic and acquired resistance to PARPi, both in vitro and in vivo. These results point to the exciting possibility of targeting the RNF114-PARP1 pathway for the treatment of homologous recombination-deficient cancers.
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Affiliation(s)
- Peng Li
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Yuanli Zhen
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Chiho Kim
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
- Department of Molecular Pharmacology and Therapeutics, Columbia University Vagelos College of Physicians and Surgeons, New York, NY 10032, USA
| | - Zhengshuai Liu
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
- Department of Molecular Pharmacology and Therapeutics, Columbia University Vagelos College of Physicians and Surgeons, New York, NY 10032, USA
| | - Jianwei Hao
- Department of Molecular Pharmacology and Therapeutics, Columbia University Vagelos College of Physicians and Surgeons, New York, NY 10032, USA
| | - Heping Deng
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Hejun Deng
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Min Zhou
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Xu-Dong Wang
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
- Department of Molecular Pharmacology and Therapeutics, Columbia University Vagelos College of Physicians and Surgeons, New York, NY 10032, USA
| | - Tian Qin
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Yonghao Yu
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
- Department of Molecular Pharmacology and Therapeutics, Columbia University Vagelos College of Physicians and Surgeons, New York, NY 10032, USA
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3
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Loughran ST, Walls D. Tagging Recombinant Proteins to Enhance Solubility and Aid Purification. Methods Mol Biol 2023; 2699:97-123. [PMID: 37646996 DOI: 10.1007/978-1-0716-3362-5_7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/01/2023]
Abstract
Protein fusion technology has had a major impact on the efficient production and purification of individual recombinant proteins. The use of genetically engineered affinity and solubility-enhancing polypeptide "tags" has a long history, and there is a considerable repertoire of these that can be used to address issues related to the expression, stability, solubility, folding, and purification of their fusion partner. In the case of large-scale proteomic studies, the development of purification procedures tailored to individual proteins is not practicable, and affinity tags have become indispensable tools for structural and functional proteomic initiatives that involve the expression of many proteins in parallel. In this chapter, the rationale and applications of a range of established and more recently developed solubility-enhancing and affinity tags is described.
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Affiliation(s)
- Sinéad T Loughran
- Department of Life and Health Sciences, School of Health and Science, Dundalk Institute of Technology, Dundalk, Louth, Ireland.
| | - Dermot Walls
- School of Biotechnology, Dublin City University, Dublin, Ireland
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4
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Proteomic analysis identifies ZMYM2 as endogenous binding partner of TBX18 protein in 293 and A549 cells. Biochem J 2021; 479:91-109. [PMID: 34935912 DOI: 10.1042/bcj20210642] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2021] [Revised: 12/15/2021] [Accepted: 12/21/2021] [Indexed: 11/17/2022]
Abstract
The TBX18 transcription factor regulates patterning and differentiation programs in the primordia of many organs yet the molecular complexes in which TBX18 resides to exert its crucial transcriptional function in these embryonic contexts have remained elusive. Here, we used 293 and A549 cells as an accessible cell source to search for endogenous protein interaction partners of TBX18 by an unbiased proteomic approach. We tagged endogenous TBX18 by CRISPR/Cas9 targeted genome editing with a triple FLAG peptide, and identified by anti-FLAG affinity purification and subsequent LC-MS analysis the ZMYM2 protein to be statistically enriched together with TBX18 in both 293 and A549 nuclear extracts. Using a variety of assays, we confirmed binding of TBX18 to ZMYM2, a component of the CoREST transcriptional corepressor complex. Tbx18 is coexpressed with Zmym2 in the mesenchymal compartment of the developing ureter of the mouse, and mutations in TBX18and in ZMYM2 were recently linked to congenital anomalies in the kidney and urinary tract (CAKUT) in line with a possible in vivo relevance of TBX18-ZMYM2 protein interaction in ureter development.
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5
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Tandem Affinity Purification (TAP) of Low-Abundance Protein Complexes in Filamentous Fungi Demonstrated Using Magnaporthe oryzae. Methods Mol Biol 2021. [PMID: 34236680 DOI: 10.1007/978-1-0716-1613-0_8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
Abstract
Protein-protein interactions underlie cellular structure and function. In recent years, a number of methods have been developed for the identification of protein complexes and component proteins involved in the control of various biological pathways. Tandem affinity purification (TAP) coupled with mass spectrometry (MS) is a powerful method enabling the isolation of high-purity native protein complexes under mild conditions by performing two sequential purification steps using two different epitope tags. In this protocol, we describe a TAP-MS methodology for identifying protein-protein interactions present at very low levels in the fungal cell. Using the 6xHis-3xFLAG double tag, we start the affinity purification process for our protein of interest using high-capacity Ni2+ columns. This allows for greatly increased sample input compared to antibody-based first-step purification in conventional TAP protocols and provides a large amount of highly concentrated and preliminarily purified protein complexes to be used in a second purification step involving FLAG immunoprecipitation. The second step greatly facilitates the capture of low-level interacting partners under in vivo conditions. Our TAP-MS method has been proven to secure the characterization of low-abundance protein complexes under physiological conditions with high efficiency, specificity, and economy in the filamentous fungus Magnaporthe oryzae and might benefit gene function and proteomics studies in plants and other research fields.
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6
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Mahmoudi Gomari M, Saraygord-Afshari N, Farsimadan M, Rostami N, Aghamiri S, Farajollahi MM. Opportunities and challenges of the tag-assisted protein purification techniques: Applications in the pharmaceutical industry. Biotechnol Adv 2020; 45:107653. [PMID: 33157154 DOI: 10.1016/j.biotechadv.2020.107653] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2020] [Revised: 10/22/2020] [Accepted: 10/29/2020] [Indexed: 01/16/2023]
Abstract
Tag-assisted protein purification is a method of choice for both academic researches and large-scale industrial demands. Application of the purification tags in the protein production process can help to save time and cost, but the design and application of tagged fusion proteins are challenging. An appropriate tagging strategy must provide sufficient expression yield and high purity for the final protein products while preserving their native structure and function. Thanks to the recent advances in the bioinformatics and emergence of high-throughput techniques (e.g. SEREX), many new tags are introduced to the market. A variety of interfering and non-interfering tags have currently broadened their application scope beyond the traditional use as a simple purification tool. They can take part in many biochemical and analytical features and act as solubility and protein expression enhancers, probe tracker for online visualization, detectors of post-translational modifications, and carrier-driven tags. Given the variability and growing number of the purification tags, here we reviewed the protein- and peptide-structured purification tags used in the affinity, ion-exchange, reverse phase, and immobilized metal ion affinity chromatographies. We highlighted the demand for purification tags in the pharmaceutical industry and discussed the impact of self-cleavable tags, aggregating tags, and nanotechnology on both the column-based and column-free purification techniques.
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Affiliation(s)
- Mohammad Mahmoudi Gomari
- Department of Medical Biotechnology, Faculty of Allied Medical Sciences, Iran University of Medical Sciences, Tehran, Iran
| | - Neda Saraygord-Afshari
- Department of Medical Biotechnology, Faculty of Allied Medical Sciences, Iran University of Medical Sciences, Tehran, Iran.
| | - Marziye Farsimadan
- Department of Biology, Faculty of Sciences, University of Guilan, Rasht, Iran
| | - Neda Rostami
- Department of Chemical Engineering, Faculty of Engineering, Arak University, Iran
| | - Shahin Aghamiri
- Student research committee, Department of medical biotechnology, School of Advanced Technologies in Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Mohammad M Farajollahi
- Department of Medical Biotechnology, Faculty of Allied Medical Sciences, Iran University of Medical Sciences, Tehran, Iran
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7
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Liu Y, Long YH, Wang SQ, Zhang YY, Li YF, Mi JS, Yu CH, Li DY, Zhang JH, Zhang XJ. JMJD6 regulates histone H2A.X phosphorylation and promotes autophagy in triple-negative breast cancer cells via a novel tyrosine kinase activity. Oncogene 2018; 38:980-997. [PMID: 30185813 DOI: 10.1038/s41388-018-0466-y] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2018] [Revised: 07/04/2018] [Accepted: 07/26/2018] [Indexed: 11/09/2022]
Abstract
Overexpression of Jumonji domain-containing 6 (JMJD6) has been reported to be associated with more aggressive breast cancer characteristics. However, the precise role of JMJD6 in breast cancer development remains unclear. Here, we demonstrate that JMJD6 has intrinsic tyrosine kinase activity and can utilize ATP and GTP as phosphate donors to phosphorylate Y39 of histone H2A.X (H2A.XY39ph). High JMJD6 levels promoted autophagy in triple negative breast cancer (TNBC) cells by regulating the expression of autophagy-related genes. The JMJD6-H2A.XY39ph axis promoted TNBC cell growth via the autophagy pathway. We show that combined inhibition of JMJD6 kinase activity and autophagy efficiently decreases TNBC growth. Together, these findings suggest an effective strategy for TNBC treatment.
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Affiliation(s)
- Yan Liu
- College of Life Science, North China University of Science and Technology, Tangshan, China.,Cancer Institute, Tangshan People's Hospital, Tangshan, China
| | - Yue-Hong Long
- College of Life Science, North China University of Science and Technology, Tangshan, China
| | - Shu-Qing Wang
- Hospital of North China University of Science and Technology, Tangshan, China.
| | - Yuan-Yue Zhang
- College of Life Science, North China University of Science and Technology, Tangshan, China.,Cancer Institute, Tangshan People's Hospital, Tangshan, China
| | - Yu-Feng Li
- Cancer Institute, Tangshan People's Hospital, Tangshan, China
| | | | | | - De-Yan Li
- People's Hospital of Zunhua, Zunhua, China
| | - Jing-Hua Zhang
- Cancer Institute, Tangshan People's Hospital, Tangshan, China.
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8
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Abstract
Protein fusion technology has had a major impact on the efficient production and purification of individual recombinant proteins. The use of genetically engineered affinity and solubility-enhancing polypeptide "tags" has increased greatly in recent years and there now exists a considerable repertoire of these that can be used to solve issues related to the expression, stability, solubility, folding, and purification of their fusion partner. In the case of large-scale proteomic studies, the development of purification procedures tailored to individual proteins is not practicable, and affinity tags have therefore become indispensable tools for structural and functional proteomic initiatives that involve the expression of many proteins in parallel. Here, the rationale and applications of a range of established and more recently developed solubility-enhancing and affinity tags is described.
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Affiliation(s)
- Sinéad T Loughran
- Department of Applied Sciences, Dundalk Institute of Technology, Dundalk, Ireland
| | - Dermot Walls
- School of Biotechnology, Dublin City University, Glasnevin, Dublin 9, Ireland.
- National Centre for Sensor Research, Dublin City University, Glasnevin, Dublin 9, Ireland.
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9
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Liu Z, Sneve M, Haroldson TA, Smith JP, Drewes LR. Regulation of Monocarboxylic Acid Transporter 1 Trafficking by the Canonical Wnt/β-Catenin Pathway in Rat Brain Endothelial Cells Requires Cross-talk with Notch Signaling. J Biol Chem 2016; 291:8059-69. [PMID: 26872974 DOI: 10.1074/jbc.m115.710277] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2016] [Indexed: 12/20/2022] Open
Abstract
The transport of monocarboxylate fuels such as lactate, pyruvate, and ketone bodies across brain endothelial cells is mediated by monocarboxylic acid transporter 1 (MCT1). Although the canonical Wnt/β-catenin pathway is required for rodent blood-brain barrier development and for the expression of associated nutrient transporters, the role of this pathway in the regulation of brain endothelial MCT1 is unknown. Here we report expression of nine members of the frizzled receptor family by the RBE4 rat brain endothelial cell line. Furthermore, activation of the canonical Wnt/β-catenin pathway in RBE4 cells via nuclear β-catenin signaling with LiCl does not alter brain endothelialMct1mRNA but increases the amount of MCT1 transporter protein. Plasma membrane biotinylation studies and confocal microscopic examination of mCherry-tagged MCT1 indicate that increased transporter results from reduced MCT1 trafficking from the plasma membrane via the endosomal/lysosomal pathway and is facilitated by decreased MCT1 ubiquitination following LiCl treatment. Inhibition of the Notch pathway by the γ-secretase inhibitorN-[N-(3,5-difluorophenacetyl)-l-alanyl]-S-phenylglycinet-butyl ester negated the up-regulation of MCT1 by LiCl, demonstrating a cross-talk between the canonical Wnt/β-catenin and Notch pathways. Our results are important because they show, for the first time, the regulation of MCT1 in cerebrovascular endothelial cells by the multifunctional canonical Wnt/β-catenin and Notch signaling pathways.
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Affiliation(s)
- Zejian Liu
- From the Department of Biomedical Sciences, University of Minnesota Medical School Duluth, Duluth, Minnesota 55812 and
| | - Mary Sneve
- From the Department of Biomedical Sciences, University of Minnesota Medical School Duluth, Duluth, Minnesota 55812 and
| | - Thomas A Haroldson
- From the Department of Biomedical Sciences, University of Minnesota Medical School Duluth, Duluth, Minnesota 55812 and
| | - Jeffrey P Smith
- the Department of Biology, Colorado State University, Pueblo, Colorado 81001
| | - Lester R Drewes
- From the Department of Biomedical Sciences, University of Minnesota Medical School Duluth, Duluth, Minnesota 55812 and
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10
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Mohammed H, Taylor C, Brown GD, Papachristou EK, Carroll JS, D'Santos CS. Rapid immunoprecipitation mass spectrometry of endogenous proteins (RIME) for analysis of chromatin complexes. Nat Protoc 2016; 11:316-26. [PMID: 26797456 DOI: 10.1038/nprot.2016.020] [Citation(s) in RCA: 187] [Impact Index Per Article: 23.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Rapid immunoprecipitation mass spectrometry of endogenous protein (RIME) is a method that allows the study of protein complexes, in particular chromatin and transcription factor complexes, in a rapid and robust manner by mass spectrometry (MS). The method can be used in parallel with chromatin immunoprecipitation-sequencing (ChIP-seq) experiments to provide information on both the cistrome and interactome for a given protein. The method uses formaldehyde fixation to stabilize protein complexes. By using antibodies against the endogenous target, the cross-linked complex is immunoprecipitated, rigorously washed, and then digested into peptides while avoiding antibody contamination (on-bead digestion). By using this method, MS identification of the target protein and several dozen interacting proteins is possible using a 100-min LC-MS/MS run. The protocol does not require substantial proteomics expertise, and it typically takes 2-3 d from the collection of material to results.
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Affiliation(s)
- Hisham Mohammed
- Cancer Research UK Cambridge Institute, University of Cambridge, Cambridge, UK
| | - Christopher Taylor
- Cancer Research UK Cambridge Institute, University of Cambridge, Cambridge, UK
| | - Gordon D Brown
- Cancer Research UK Cambridge Institute, University of Cambridge, Cambridge, UK
| | | | - Jason S Carroll
- Cancer Research UK Cambridge Institute, University of Cambridge, Cambridge, UK
| | - Clive S D'Santos
- Cancer Research UK Cambridge Institute, University of Cambridge, Cambridge, UK
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11
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When less becomes more: Optimization of protein expression in HEK293–EBNA1 cells using plasmid titration – A case study for NLRs. Protein Expr Purif 2014; 99:27-34. [DOI: 10.1016/j.pep.2014.03.010] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2013] [Revised: 03/14/2014] [Accepted: 03/17/2014] [Indexed: 11/19/2022]
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12
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Schäffer U, Baumeister R, Schulze E. Targeted purification of SnAvi-tagged proteins. Methods Mol Biol 2014; 1177:163-74. [PMID: 24943322 DOI: 10.1007/978-1-4939-1034-2_13] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/21/2023]
Abstract
Tandem affinity purification (TAP) is a powerful technique to identify protein complex members. The modular composition of TAP-tags allows two sequential protein enrichment steps and thereby drastically reduces the amount of contaminants. Here, we describe the application of the SnAvi-tag-a TAP-tag useful in different expression systems. Due to its modular composition, this tag is multifunctional and facilitates among others the in vivo visualization of tagged proteins and their cell type specific activation.
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Affiliation(s)
- Ursula Schäffer
- Institute for Biology 3, University of Freiburg, Schänzlestr. 4, 79104, Freiburg, Germany,
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13
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Chen YS, Bastidas RJ, Saka HA, Carpenter VK, Richards KL, Plano GV, Valdivia RH. The Chlamydia trachomatis type III secretion chaperone Slc1 engages multiple early effectors, including TepP, a tyrosine-phosphorylated protein required for the recruitment of CrkI-II to nascent inclusions and innate immune signaling. PLoS Pathog 2014; 10:e1003954. [PMID: 24586162 PMCID: PMC3930595 DOI: 10.1371/journal.ppat.1003954] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2013] [Accepted: 01/10/2014] [Indexed: 02/06/2023] Open
Abstract
Chlamydia trachomatis, the causative agent of trachoma and sexually transmitted infections, employs a type III secretion (T3S) system to deliver effector proteins into host epithelial cells to establish a replicative vacuole. Aside from the phosphoprotein TARP, a Chlamydia effector that promotes actin re-arrangements, very few factors mediating bacterial entry and early inclusion establishment have been characterized. Like many T3S effectors, TARP requires a chaperone (Slc1) for efficient translocation into host cells. In this study, we defined proteins that associate with Slc1 in invasive C. trachomatis elementary bodies (EB) by immunoprecipitation coupled with mass spectrometry. We identified Ct875, a new Slc1 client protein and T3S effector, which we renamed TepP (Translocated early phosphoprotein). We provide evidence that T3S effectors form large molecular weight complexes with Scl1 in vitro and that Slc1 enhances their T3S-dependent secretion in a heterologous Yersinia T3S system. We demonstrate that TepP is translocated early during bacterial entry into epithelial cells and is phosphorylated at tyrosine residues by host kinases. However, TepP phosphorylation occurs later than TARP, which together with the finding that Slc1 preferentially engages TARP in EBs leads us to postulate that these effectors are translocated into the host cell at different stages during C. trachomatis invasion. TepP co-immunoprecipitated with the scaffolding proteins CrkI-II during infection and Crk was recruited to EBs at entry sites where it remained associated with nascent inclusions. Importantly, C. trachomatis mutants lacking TepP failed to recruit CrkI-II to inclusions, providing genetic confirmation of a direct role for this effector in the recruitment of a host factor. Finally, endocervical epithelial cells infected with a tepP mutant showed altered expression of a subset of genes associated with innate immune responses. We propose a model wherein TepP acts downstream of TARP to recruit scaffolding proteins at entry sites to initiate and amplify signaling cascades important for the regulation of innate immune responses to Chlamydia.
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Affiliation(s)
- Yi-Shan Chen
- Department of Molecular Genetics and Microbiology and Center for Microbial Pathogenesis, Duke University Medical Center, Durham, North Carolina, United States of America
- Department of Biochemistry, Duke University Medical Center, Durham, North Carolina, United States of America
| | - Robert J. Bastidas
- Department of Molecular Genetics and Microbiology and Center for Microbial Pathogenesis, Duke University Medical Center, Durham, North Carolina, United States of America
| | - Hector A. Saka
- Department of Molecular Genetics and Microbiology and Center for Microbial Pathogenesis, Duke University Medical Center, Durham, North Carolina, United States of America
| | - Victoria K. Carpenter
- Department of Molecular Genetics and Microbiology and Center for Microbial Pathogenesis, Duke University Medical Center, Durham, North Carolina, United States of America
| | - Kristian L. Richards
- Department of Microbiology and Immunology, University of Miami Miller School of Medicine, Miami, Florida, United States of America
| | - Gregory V. Plano
- Department of Microbiology and Immunology, University of Miami Miller School of Medicine, Miami, Florida, United States of America
| | - Raphael H. Valdivia
- Department of Molecular Genetics and Microbiology and Center for Microbial Pathogenesis, Duke University Medical Center, Durham, North Carolina, United States of America
- * E-mail:
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14
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An efficient fluorescent protein-based multifunctional affinity purification approach in mammalian cells. Methods Mol Biol 2014; 1177:175-91. [PMID: 24943323 DOI: 10.1007/978-1-4939-1034-2_14] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Knowledge of an individual protein's modifications, binding partners, and localization is essential for understanding complex biological networks. We recently described a fluorescent protein-based (mVenus) multifunctional affinity purification (MAP) tag that can be used both to purify a given protein and determine its localization (Ma et al., Mol Cell Proteomics 11:501-511, 2012). MAP purified protein complexes can be further analyzed to identify binding partners and posttranslational modifications by LC-MS/MS. The MAP approach offers rapid FACS-selection of stable clonal cell lines based on the expression level/fluorescence of the MAP-protein fusion. The MAP tag is highly efficient and shows little variability between proteins. Here we describe the general MAP purification method in detail, and show how it can be applied to a specific protein using the human Cdc14B phosphatase as an example.
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15
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Trinkle-Mulcahy L. Resolving protein interactions and complexes by affinity purification followed by label-based quantitative mass spectrometry. Proteomics 2012; 12:1623-38. [PMID: 22610586 DOI: 10.1002/pmic.201100438] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Label-based quantitative mass spectrometry analysis of affinity purified complexes, with its built-in negative controls and relative ease of use, is an increasingly popular choice for defining protein-protein interactions and multiprotein complexes. This approach, which differentially labels proteins/peptides from two or more populations and combines them prior to analysis, permits direct comparison of a protein pulldown (e.g. affinity purified tagged protein) to that of a control pulldown (e.g. affinity purified tag alone) in a single mass spectrometry (MS) run, thus avoiding the variability inherent in separate runs. The use of quantitative techniques has been driven in large part by significant improvements in the resolution and sensitivity of high-end mass spectrometers. Importantly, the availability of commercial reagents and open source identification/quantification software has made these powerful techniques accessible to nonspecialists. Benefits and drawbacks of the most popular labeling-based approaches are discussed here, and key steps/strategies for the use of labeling in quantitative immunoprecipitation experiments detailed.
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Affiliation(s)
- Laura Trinkle-Mulcahy
- Department of Cellular & Molecular Medicine, University of Ottawa, Ottawa, ON, Canada.
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16
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Halff EF, Diebolder CA, Versteeg M, Schouten A, Brondijk THC, Huizinga EG. Formation and structure of a NAIP5-NLRC4 inflammasome induced by direct interactions with conserved N- and C-terminal regions of flagellin. J Biol Chem 2012; 287:38460-72. [PMID: 23012363 DOI: 10.1074/jbc.m112.393512] [Citation(s) in RCA: 124] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
The NOD-like receptors NAIP5 and NLRC4 play an essential role in the innate immune response to the bacterial tail protein flagellin. Upon flagellin detection, NAIP5 and NLRC4 form a hetero-oligomeric inflammasome that induces caspase-1-dependent cell death. So far, both the mechanism of formation of the NAIP5-NLRC4 inflammasome and its structure are poorly understood. In this study we combine inflammasome reconstitution in HEK293 cells, purification of inflammasome components, and negative stain electron microscopy to address these issues. We find that a Salmonella typhimurium flagellin fragment comprising the D0 domain and the neighboring spoke region is able to co-precipitate NAIP5 and induce formation of the NAIP5-NLRC4 inflammasome. Comparison with smaller fragments indicates that flagellin recognition is mediated by its C-terminal residues as well as the spoke region. We reconstitute the inflammasome from purified flagellin, NAIP5, and NLRC4, thus proving that no other cellular components are required for its formation. Electron micrographs of the purified inflammasome provide unprecedented insight into its architecture, revealing disk-like complexes consisting of 11 or 12 protomers in which NAIP5 and NLRC4 appear to occupy equivalent positions. On the basis of our data, we propose a model for inflammasome formation wherein direct interaction of flagellin with a single NAIP5 induces the recruitment and progressive incorporation of NLRC4, resulting in the formation of a hetero-oligomeric inflammasome.
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Affiliation(s)
- Els F Halff
- Crystal and Structural Chemistry, Bijvoet Center for Biomolecular Research, Department of Chemistry, Faculty of Science, Utrecht University, 3584 CH Utrecht, The Netherlands
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17
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Pepper A, Bhogal B, Jongens T. Tandem Affinity Purification in Drosophila Heads and Ovaries. Bio Protoc 2012; 2:e245. [PMID: 27042686 DOI: 10.21769/bioprotoc.245] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022] Open
Abstract
Tandem affinity purification (TAP) (Pugi et al., 2001; Rigaut et al., 1999) is a method that uses a tagging approach of a target protein of interest for a two-step purification scheme in order to pull down protein complexes under native conditions and expression levels. The TAP tag consists of three components: a calmodulin-binding peptide, a Tobacco etch virus (TEV) protease cleavage site and Protein A which is an immunoglobulin G (IgG)-binding domain. This protocol was modified from the original methodology used in yeast cells (Pugi et al., 2001; Rigaut et al., 1999) for isolation of protein complexes from Drosophila heads and ovaries expressing a TAP tagged protein of interest. To determine in vivo binding partners of the Drosophila fragile X protein (dFMR1), we developed a transgenic strain of flies expressing a recombinant form of dFMR1 with a carboxy-terminal TAP tag (Tsai and Carstens, 2006). To ensure that the construct was expressed at wild-type levels, we engineered this form of the tagged protein in the context of a genomic rescue construct that rescued a mutant sterility phenotype. The purification process was performed using mild conditions to maintain native protein interactions. For TAP methods in Drosophila S2 cell culture, we have successfully used a protocol previously published by Tsai and Carstens (Tsai and Carstens, 2006; Bhogal et al., 2011).
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Affiliation(s)
- Anita Pepper
- Department of Genetics, The Perelman School of Medicine at the University of Pennsylvania, Philadelphia, USA
| | - Balpreet Bhogal
- Department of Genetics, The Perelman School of Medicine at the University of Pennsylvania, Philadelphia, USA
| | - Thomas Jongens
- Department of Genetics, The Perelman School of Medicine at the University of Pennsylvania, Philadelphia, USA
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18
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Lokireddy S, Wijesoma IW, Sze SK, McFarlane C, Kambadur R, Sharma M. Identification of atrogin-1-targeted proteins during the myostatin-induced skeletal muscle wasting. Am J Physiol Cell Physiol 2012; 303:C512-29. [PMID: 22673621 DOI: 10.1152/ajpcell.00402.2011] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Atrogin-1, a muscle-specific E3 ligase, targets MyoD for degradation through the ubiquitin-proteasome-mediated system. Myostatin, a member of the transforming growth factor-β superfamily, potently inhibits myogenesis by lowering MyoD levels. While atrogin-1 is upregulated by myostatin, it is currently unknown whether atrogin-1 plays a role in mediating myostatin signaling to regulate myogenesis. In this report, we have confirmed that atrogin-1 increasingly interacts with MyoD upon recombinant human myostatin (hMstn) treatment. The absence of atrogin-1, however, led to elevated MyoD levels and permitted the differentiation of atrogin-1(-/-) primary myoblast cultures despite the presence of exogenous myostatin. Furthermore, inactivation of atrogin-1 rescued myoblasts from growth inhibition by hMstn. Therefore, these results highlight the central role of atrogin-1 in regulating myostatin signaling during myogenesis. Currently, there are only two known targets of atrogin-1. Thus, we next characterized the associated proteins of atrogin-1 in control and hMstn-treated C2C12 cell cultures by stably expressing tagged atrogin-1 in myoblasts and myotubes, and sequencing the coimmunoprecipitated proteome. We found that atrogin-1 putatively interacts with sarcomeric proteins, transcriptional factors, metabolic enzymes, components of translation, and spliceosome formation. In addition, we also identified that desmin and vimentin, two components of the intermediate filament in muscle, directly interacted with and were degraded by atrogin-1 in response to hMstn. In summary, the muscle wasting effects of the myostatin-atrogin-1 axis are not only limited to the degradation of MyoD and eukaryotic translation initiation factor 3 subunit f, but also encompass several proteins that are involved in a wide variety of cellular activities in the muscle.
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Small heat-shock protein HSPB1 mutants stabilize microtubules in Charcot-Marie-Tooth neuropathy. J Neurosci 2011; 31:15320-8. [PMID: 22031878 DOI: 10.1523/jneurosci.3266-11.2011] [Citation(s) in RCA: 85] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Mutations in the small heat shock protein HSPB1 (HSP27) are causative for Charcot-Marie-Tooth (CMT) neuropathy. We previously showed that a subset of these mutations displays higher chaperone activity and enhanced affinity to client proteins. We hypothesized that this excessive binding property might cause the HSPB1 mutant proteins to disturb the function of proteins essential for the maintenance or survival of peripheral neurons. In the present work, we explored this hypothesis further and compared the protein complexes formed by wild-type and mutant HSPB1. Tubulin came out as the most striking differential interacting protein, with hyperactive mutants binding more strongly to both tubulin and microtubules. This anomalous binding leads to a stabilization of the microtubule network in a microtubule-associated protein-like manner as reflected by resistance to cold depolymerization, faster network recovery after nocodazole treatment, and decreased rescue and catastrophe rates of individual microtubules. In a transgenic mouse model for mutant HSPB1 that recapitulates all features of CMT, we could confirm the enhanced interaction of mutant HSPB1 with tubulin. Increased stability of the microtubule network was also clear in neurons isolated from these mice. Since neuronal cells are particularly vulnerable to disturbances in microtubule dynamics, this mechanism might explain the neuron-specific CMT phenotype caused by HSPB1 mutations.
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20
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Bhogal B, Jepson JE, Savva YA, Pepper ASR, Reenan RA, Jongens TA. Modulation of dADAR-dependent RNA editing by the Drosophila fragile X mental retardation protein. Nat Neurosci 2011; 14:1517-24. [PMID: 22037499 PMCID: PMC3225737 DOI: 10.1038/nn.2950] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2011] [Accepted: 09/09/2011] [Indexed: 11/09/2022]
Abstract
Loss of FMR1 gene function results in fragile X syndrome (FXS), the most common heritable form of intellectual disability. The protein encoded from this locus (FMRP) is an RNA binding protein thought to primarily act as a translational regulator, however recent studies implicate FMRP in other mechanisms of gene regulation. Here, we demonstrate that the Drosophila fragile X homolog (dFMR1) biochemically interacts with the A-to-I RNA editing enzyme, dADAR. We found that dAdar and dfmr1 mutant larvae exhibit distinct morphological neuromuscular junction (NMJ) defects. Epistasis experiments based on these phenotypic differences suggest that dAdar acts downstream of dfmr1 and that dFMR1 modulates dADAR activity. Furthermore, sequence analyses revealed that loss or overexpression of dFMR1 affects editing efficiency on certain dADAR targets with defined roles in synaptic transmission. These results link dFMR1 with the RNA editing pathway and suggest that proper NMJ synaptic architecture requires modulation of dADAR activity by dFMR1.
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Affiliation(s)
- Balpreet Bhogal
- Department of Genetics, The Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania, USA
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21
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Zhao HY, Zhang YJ, Dai H, Zhang Y, Shen YF. CARM1 mediates modulation of Sox2. PLoS One 2011; 6:e27026. [PMID: 22046437 PMCID: PMC3203945 DOI: 10.1371/journal.pone.0027026] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2011] [Accepted: 10/09/2011] [Indexed: 01/06/2023] Open
Abstract
Sox2 is a key component of the transcription factor network that maintains the pluripotent state of embryonic stem cells (ESCs). Sox2 is regulated by multiple post-translational modifications, including ubiquitination, sumoylation, acetylation and phosphorylation. Here we report that Sox2 is in association with and methylated by coactivator-associated arginine methyltransferase 1 (CARM1), a protein arginine methyltransferase that plays a pivotal role in ESCs. We found that CARM1 facilitates Sox2-mediated transactivation and directly methylates Sox2 at arginine 113. This methylation event enhances Sox2 self-association. Furthermore, the physiological retention of Sox2 on chromatin restricts the Sox2 methylation level. Our study reveals the direct regulation of Sox2 by CARM1 that sheds lights on how arginine methylation signals are integrated into the pluripotent transcription factor network.
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Affiliation(s)
- Hai-yong Zhao
- National Laboratory of Medical Molecular Biology, Department of Biochemistry and Molecular Biology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, China
| | - Yan-jun Zhang
- National Laboratory of Medical Molecular Biology, Department of Biochemistry and Molecular Biology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, China
| | - Hui Dai
- National Laboratory of Medical Molecular Biology, Department of Biochemistry and Molecular Biology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, China
| | - Ye Zhang
- National Laboratory of Medical Molecular Biology, Department of Biochemistry and Molecular Biology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, China
- * E-mail: (YZ); (Y-FS)
| | - Yu-fei Shen
- National Laboratory of Medical Molecular Biology, Department of Biochemistry and Molecular Biology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, China
- * E-mail: (YZ); (Y-FS)
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22
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Lokireddy S, McFarlane C, Ge X, Zhang H, Sze SK, Sharma M, Kambadur R. Myostatin induces degradation of sarcomeric proteins through a Smad3 signaling mechanism during skeletal muscle wasting. Mol Endocrinol 2011; 25:1936-49. [PMID: 21964591 DOI: 10.1210/me.2011-1124] [Citation(s) in RCA: 100] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Ubiquitination-mediated proteolysis is a hallmark of skeletal muscle wasting manifested in response to negative growth factors, including myostatin. Thus, the characterization of signaling mechanisms that induce the ubiquitination of intracellular and sarcomeric proteins during skeletal muscle wasting is of great importance. We have recently characterized myostatin as a potent negative regulator of myogenesis and further demonstrated that elevated levels of myostatin in circulation results in the up-regulation of the muscle-specific E3 ligases, Atrogin-1 and muscle ring finger protein 1 (MuRF1). However, the exact signaling mechanisms by which myostatin regulates the expression of Atrogin-1 and MuRF1, as well as the proteins targeted for degradation in response to excess myostatin, remain to be elucidated. In this report, we have demonstrated that myostatin signals through Smad3 (mothers against decapentaplegic homolog 3) to activate forkhead box O1 and Atrogin-1 expression, which further promotes the ubiquitination and subsequent proteasome-mediated degradation of critical sarcomeric proteins. Smad3 signaling was dispensable for myostatin-dependent overexpression of MuRF1. Although down-regulation of Atrogin-1 expression rescued approximately 80% of sarcomeric protein loss induced by myostatin, only about 20% rescue was seen when MuRF1 was silenced, implicating that Atrogin-1 is the predominant E3 ligase through which myostatin manifests skeletal muscle wasting. Furthermore, we have highlighted that Atrogin-1 not only associates with myosin heavy and light chain, but it also ubiquitinates these sarcomeric proteins. Based on presented data we propose a model whereby myostatin induces skeletal muscle wasting through targeting sarcomeric proteins via Smad3-mediated up-regulation of Atrogin-1 and forkhead box O1.
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23
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Oo ML, Chang SH, Thangada S, Wu MT, Rezaul K, Blaho V, Hwang SI, Han DK, Hla T. Engagement of S1P₁-degradative mechanisms leads to vascular leak in mice. J Clin Invest 2011; 121:2290-300. [PMID: 21555855 DOI: 10.1172/jci45403] [Citation(s) in RCA: 182] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2010] [Accepted: 03/30/2011] [Indexed: 02/02/2023] Open
Abstract
GPCR inhibitors are highly prevalent in modern therapeutics. However, interference with complex GPCR regulatory mechanisms leads to both therapeutic efficacy and adverse effects. Recently, the sphingosine-1-phosphate (S1P) receptor inhibitor FTY720 (also known as Fingolimod), which induces lymphopenia and prevents neuroinflammation, was adopted as a disease-modifying therapeutic in multiple sclerosis. Although highly efficacious, dose-dependent increases in adverse events have tempered its utility. We show here that FTY720P induces phosphorylation of the C-terminal domain of S1P receptor 1 (S1P₁) at multiple sites, resulting in GPCR internalization, polyubiquitinylation, and degradation. We also identified the ubiquitin E3 ligase WWP2 in the GPCR complex and demonstrated its requirement in FTY720-induced receptor degradation. GPCR degradation was not essential for the induction of lymphopenia, but was critical for pulmonary vascular leak in vivo. Prevention of receptor phosphorylation, internalization, and degradation inhibited vascular leak, which suggests that discrete mechanisms of S1P receptor regulation are responsible for the efficacy and adverse events associated with this class of therapeutics.
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Affiliation(s)
- Myat Lin Oo
- Center for Vascular Biology, Department of Pathology and Laboratory Medicine, Weill Cornell Medical College, Cornell University, New York, New York 10065, USA
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24
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Li Y, Franklin S, Zhang MJ, Vondriska TM. Highly efficient purification of protein complexes from mammalian cells using a novel streptavidin-binding peptide and hexahistidine tandem tag system: application to Bruton's tyrosine kinase. Protein Sci 2011; 20:140-9. [PMID: 21080425 DOI: 10.1002/pro.546] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Tandem affinity purification (TAP) is a generic approach for the purification of protein complexes. The key advantage of TAP is the engineering of dual affinity tags that, when attached to the protein of interest, allow purification of the target protein along with its binding partners through two consecutive purification steps. The tandem tag used in the original method consists of two IgG-binding units of protein A from Staphylococcus aureus (ProtA) and the calmodulin-binding peptide (CBP), and it allows for recovery of 20-30% of the bait protein in yeast. When applied to higher eukaryotes, however, this classical TAP tag suffers from low yields. To improve protein recovery in systems other than yeast, we describe herein the development of a three-tag system comprised of CBP, streptavidin-binding peptide (SBP) and hexa-histidine. We illustrate the application of this approach for the purification of human Bruton's tyrosine kinase (Btk), which results in highly efficient binding and elution of bait protein in both purification steps (>50% recovery). Combined with mass spectrometry for protein identification, this TAP strategy facilitated the first nonbiased analysis of Btk interacting proteins. The high efficiency of the SBP-His₆ purification allows for efficient recovery of protein complexes formed with a target protein of interest from a small amount of starting material, enhancing the ability to detect low abundance and transient interactions in eukaryotic cell systems.
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Affiliation(s)
- Yifeng Li
- Department of Anesthesiology, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, USA
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25
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Gupta S, Wallqvist A, Bondugula R, Ivanic J, Reifman J. Unraveling the conundrum of seemingly discordant protein-protein interaction datasets. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2011; 2010:783-6. [PMID: 21096109 DOI: 10.1109/iembs.2010.5626490] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Most high-throughput experimental results of protein-protein interactions (PPIs) are seemingly inconsistent with each other. In this article, we re-evaluated these contradictions within the context of the underlying domain-domain interactions (DDIs) for two Escherichia coli and four Saccharomyces cerevisiae PPI datasets derived from high-throughput (yeast two-hybrid and tandem affinity purification) experimental platforms. For shared DDIs across pairs of compared datasets, we observed a remarkably high pair-wise correlation (Pearson correlation coefficient between 0.80 and 0.84) between datasets of the same organism derived from the same experimental platform. To a lesser degree, this concordance also held true for more general inter-platform and intra-species comparisons (Pearson correlation coefficient between 0.52 and 0.89). Thus, although varying experimental conditions can influence the ability of individual proteins to interact and, therefore, create apparent differences among PPIs, the physical nature of the underlying interactions, captured by DDIs, is the same and can be used to model and predict PPIs.
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Affiliation(s)
- Shobhit Gupta
- Department of Defense Biotechnology High Performance Computing Software Applications Institute, Telemedicine and Advanced Technology Research Center, U.S. Army Medical Research and Materiel Command, Fort Detrick, MD, USA
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26
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Li Y. The tandem affinity purification technology: an overview. Biotechnol Lett 2011; 33:1487-99. [PMID: 21424840 DOI: 10.1007/s10529-011-0592-x] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2011] [Accepted: 03/08/2011] [Indexed: 02/07/2023]
Abstract
Tandem affinity purification (TAP) is a methodology for the isolation of protein complexes from endogenous sources. It involves incorporation of a dual-affinity tag into the protein of interest and introduction of the construct into desired cell lines or organisms. Using the two affinity handles, the protein complex assembled under physiological conditions, which contains the tagged target protein and its interacting partners, can be isolated by a sequential purification scheme. Compared with single-step purification, TAP greatly reduces non-specific background and isolates protein complexes with higher purity. TAP-based protein retrieval plus mass spectrometry-based analysis has become a standard approach for identification and characterization of multi-protein complexes. The present article gives an overview of the TAP method, with a focus on its key feature-the dual-affinity tag. In addition, the application of this technology in various systems is briefly discussed.
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Affiliation(s)
- Yifeng Li
- Protein Production Core Facility, Department of Biochemistry, University of Texas Health Science Center at San Antonio, 7303 Floyd Curl Drive, San Antonio, TX 78229, USA.
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27
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Walls D, Loughran ST. Tagging recombinant proteins to enhance solubility and aid purification. Methods Mol Biol 2011; 681:151-175. [PMID: 20978965 DOI: 10.1007/978-1-60761-913-0_9] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Protein fusion technology has enormously facilitated the efficient production and purification of individual recombinant proteins. The use of genetically engineered affinity and solubility-enhancing polypeptide "tags" has increased greatly in recent years and there now exists a considerable repertoire of these that can be used to solve issues related to the expression, stability, solubility, folding, and purification of their fusion partner. In the case of large-scale proteomic studies, the development of purification procedures tailored to individual proteins is not practicable, and affinity tags have therefore become indispensable tools for structural and functional proteomic initiatives that involve the expression of many proteins in parallel. Here, the rationale and applications of a range of established and more recently developed solubility-enhancing and affinity tags are outlined.
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Affiliation(s)
- Dermot Walls
- School of Biotechnology and National Centre for Sensor Research, Dublin City University, Dublin, Ireland.
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28
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Almeida-Souza L, Goethals S, de Winter V, Dierick I, Gallardo R, Van Durme J, Irobi J, Gettemans J, Rousseau F, Schymkowitz J, Timmerman V, Janssens S. Increased monomerization of mutant HSPB1 leads to protein hyperactivity in Charcot-Marie-Tooth neuropathy. J Biol Chem 2010; 285:12778-86. [PMID: 20178975 PMCID: PMC2857091 DOI: 10.1074/jbc.m109.082644] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Small heat shock proteins are molecular chaperones capable of maintaining denatured proteins in a folding-competent state. We have previously shown that missense mutations in the small heat shock protein HSPB1 (HSP27) cause distal hereditary motor neuropathy and axonal Charcot-Marie-Tooth disease. Here we investigated the biochemical consequences of HSPB1 mutations that are known to cause peripheral neuropathy. In contrast to other chaperonopathies, our results revealed that particular HSPB1 mutations presented higher chaperone activity compared with wild type. Hyperactivation of HSPB1 was accompanied by a change from its wild-type dimeric state to a monomer without dissociation of the 24-meric state. Purification of protein complexes from wild-type and HSPB1 mutants showed that the hyperactive isoforms also presented enhanced binding to client proteins. Furthermore, we show that the wild-type HSPB1 protein undergoes monomerization during heat-shock activation, strongly suggesting that the monomer is the active form of the HSPB1 protein.
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Affiliation(s)
- Leonardo Almeida-Souza
- Peripheral Neuropathy Group, VIB Department of Molecular Genetics and University of Antwerp, 2610 Antwerp, Belgium
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29
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Abstract
TAP (tandem affinity purification) allows rapid and clean isolation of a tagged protein along with its interacting partners from cell lysates. Initially developed in yeast, the TAP method has subsequently been adapted to other cells and organisms. In combination with MS analysis, this method has become an indispensable tool for systematic identification of target-associated protein complexes. The key feature of TAP is the use of a dual-affinity tag, which is fused to the protein of interest. The original TAP tag consisted of two IgG-binding units of Protein A of Staphylococcus aureus and the calmodulin-binding peptide. As the technique has been widely exploited, a number of alternative TAP tags based on other affinity handles have been developed. The present review gives an overview of the various tag combinations for TAP with a highlight on those alternatives that result in improved yields or unique features. The information provided should assist in the selection and development of TAP tags for specific applications.
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30
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Schäffer U, Schlosser A, Müller KM, Schäfer A, Katava N, Baumeister R, Schulze E. SnAvi--a new tandem tag for high-affinity protein-complex purification. Nucleic Acids Res 2010; 38:e91. [PMID: 20047968 PMCID: PMC2847239 DOI: 10.1093/nar/gkp1178] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Systematic tandem-affinity-purification (TAP) of protein complexes was tremendously successful in yeast and has changed the general concept of how we understand protein function in eukaryotic cells. The transfer of this method to other model organisms has been difficult and may require specific adaptations. We were especially interested to establish a cell-type-specific TAP system for Caenorhabditis elegans, a model animal well suited to high-throughput analysis, proteomics and systems biology. By combining the high-affinity interaction between in vivo biotinylated target-proteins and streptavidin with the usage of a newly identified epitope of the publicly shared SB1 monoclonal antibody we created a novel in vivo fluorescent tag, the SnAvi-Tag. We show the versatile application of the SnAvi-Tag in Escherichia coli, vertebrate cells and in C. elegans for tandem affinity purification of protein complexes, western blotting and also for the in vivo sub-cellular localization of labelled proteins.
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Affiliation(s)
- Ursula Schäffer
- Bioinformatics and Molecular Genetics, ZBMZ, Institute for Biology, ZBSA-Center for Systems Biology, Albert-Ludwigs-Universitaet Freiburg, 79104 Freiburg, Germany
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31
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Babu M, Butland G, Pogoutse O, Li J, Greenblatt JF, Emili A. Sequential peptide affinity purification system for the systematic isolation and identification of protein complexes from Escherichia coli. Methods Mol Biol 2009; 564:373-400. [PMID: 19544035 DOI: 10.1007/978-1-60761-157-8_22] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Biochemical purification of affinity-tagged proteins in combination with mass spectrometry methods is increasingly seen as a cornerstone of systems biology, as it allows for the systematic genome-scale characterization of macromolecular protein complexes, representing demarcated sets of stably interacting protein partners. Accurate and sensitive identification of both the specific and shared polypeptide components of distinct complexes requires purification to near homogeneity. To this end, a sequential peptide affinity (SPA) purification system was developed to enable the rapid and efficient isolation of native Escherichia coli protein complexes (J Proteome Res 3:463-468, 2004). SPA purification makes use of a dual-affinity tag, consisting of three modified FLAG sequences (3X FLAG) and a calmodulin binding peptide (CBP), spaced by a cleavage site for tobacco etch virus (TEV) protease (J Proteome Res 3:463-468, 2004). Using the lambda-phage Red homologous recombination system (PNAS 97:5978-5983, 2000), a DNA cassette, encoding the SPA-tag and a selectable marker flanked by gene-specific targeting sequences, is introduced into a selected locus in the E. coli chromosome so as to create a C-terminal fusion with the protein of interest. This procedure aims for near-endogenous levels of tagged protein production in the recombinant bacteria to avoid spurious, non-specific protein associations (J Proteome Res 3:463-468, 2004). In this chapter, we describe a detailed, optimized protocol for the tagging, purification, and subsequent mass spectrometry-based identification of the subunits of even low-abundance bacterial protein complexes isolated as part of an ongoing large-scale proteomic study in E. coli (Nature 433:531-537, 2005).
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Affiliation(s)
- Mohan Babu
- Banting and Best Department of Medical Research, University of Toronto, Donnelly Center for Cellular and Biomolecular Research, 160 College Street, Toronto, ON, Canada M5S 3E1
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32
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Gopalakrishnan S, Sullivan BA, Trazzi S, Della Valle G, Robertson KD. DNMT3B interacts with constitutive centromere protein CENP-C to modulate DNA methylation and the histone code at centromeric regions. Hum Mol Genet 2009; 18:3178-93. [PMID: 19482874 PMCID: PMC2722982 DOI: 10.1093/hmg/ddp256] [Citation(s) in RCA: 115] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2009] [Accepted: 05/27/2009] [Indexed: 12/31/2022] Open
Abstract
DNA methylation is an epigenetically imposed mark of transcriptional repression that is essential for maintenance of chromatin structure and genomic stability. Genome-wide methylation patterns are mediated by the combined action of three DNA methyltransferases: DNMT1, DNMT3A and DNMT3B. Compelling links exist between DNMT3B and chromosome stability as emphasized by the mitotic defects that are a hallmark of ICF syndrome, a disease arising from germline mutations in DNMT3B. Centromeric and pericentromeric regions are essential for chromosome condensation and the fidelity of segregation. Centromere regions contain distinct epigenetic marks, including dense DNA hypermethylation, yet the mechanisms by which DNA methylation is targeted to these regions remains largely unknown. In the present study, we used a yeast two-hybrid screen and identified a novel interaction between DNMT3B and constitutive centromere protein CENP-C. CENP-C is itself essential for mitosis. We confirm this interaction in mammalian cells and map the domains responsible. Using siRNA knock downs, bisulfite genomic sequencing and ChIP, we demonstrate for the first time that CENP-C recruits DNA methylation and DNMT3B to both centromeric and pericentromeric satellite repeats and that CENP-C and DNMT3B regulate the histone code in these regions, including marks characteristic of centromeric chromatin. Finally, we demonstrate that loss of CENP-C or DNMT3B leads to elevated chromosome misalignment and segregation defects during mitosis and increased transcription of centromeric repeats. Taken together, our data reveal a novel mechanism by which DNA methylation is targeted to discrete regions of the genome and contributes to chromosomal stability.
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Affiliation(s)
- Suhasni Gopalakrishnan
- Department of Biochemistry and Molecular Biology, University of Florida, Box 100245, Gainesville, FL 32610, USA
| | - Beth A. Sullivan
- Department of Molecular Genetics and Microbiology, Duke University, 101 Science Dr, Durham, NC 27708, USA
| | - Stefania Trazzi
- Department of Human and General Physiology, P.zza Porta San Donato, 40126 Bologna, Italy
| | | | - Keith D. Robertson
- Department of Biochemistry and Molecular Biology, University of Florida, Box 100245, Gainesville, FL 32610, USA
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Nabet B, Tsai A, Tobias JW, Carstens RP. Identification of a putative network of actin-associated cytoskeletal proteins in glomerular podocytes defined by co-purified mRNAs. PLoS One 2009; 4:e6491. [PMID: 19652713 PMCID: PMC2714980 DOI: 10.1371/journal.pone.0006491] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2009] [Accepted: 06/25/2009] [Indexed: 11/30/2022] Open
Abstract
The glomerular podocyte is a highly specialized and polarized kidney cell type that contains major processes and foot processes that extend from the cell body. Foot processes from adjacent podocytes form interdigitations with those of adjacent cells, thereby creating an essential intercellular junctional domain of the renal filtration barrier known as the slit diaphragm. Interesting parallels have been drawn between the slit diaphragm and other sites of cell-cell contact by polarized cells. Notably mutations in several genes encoding proteins localized to the foot processes can lead to proteinuria and kidney failure. Mutations in the Wilm's tumor gene (WT1) can also lead to kidney disease and one isoform of WT1, WT1(+KTS), has been proposed to regulate gene expression post-transcriptionally. We originally sought to identify mRNAs associated with WT1(+KTS) through an RNA immunoprecipitation and microarray approach, hypothesizing that the proteins encoded by these mRNAs might be important for podocyte morphology and function. We identified a subset of mRNAs that were remarkably enriched for transcripts encoding actin-binding proteins and other cytoskeletal proteins including several that are localized at or near the slit diaphragm. Interestingly, these mRNAs included those of α-actinin-4 and non-muscle myosin IIA that are mutated in genetic forms of kidney disease. However, isolation of the mRNAs occurred independently of the expression of WT1, suggesting that the identified mRNAs were serendipitously co-purified on the basis of co-association in a common subcellular fraction. Mass spectroscopy revealed that other components of the actin cytoskeleton co-purified with these mRNAs, namely actin, tubulin, and elongation factor 1α. We propose that these mRNAs encode a number of proteins that comprise a highly specialized protein interactome underlying the slit diaphragm. Collectively, these gene products and their interactions may prove to be important for the structural integrity of the actin cytoskeleton in podocytes as well as other polarized cell types.
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Affiliation(s)
- Behnam Nabet
- Department of Medicine, University of Pennsylvania School of Medicine, Philadelphia, PA, USA
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Babu M, Krogan NJ, Awrey DE, Emili A, Greenblatt JF. Systematic characterization of the protein interaction network and protein complexes in Saccharomyces cerevisiae using tandem affinity purification and mass spectrometry. Methods Mol Biol 2009; 548:187-207. [PMID: 19521826 DOI: 10.1007/978-1-59745-540-4_11] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/24/2023]
Abstract
Defining protein complexes is a vital aspect of cell biology because cellular processes are often carried out by stable protein complexes and their characterization often provides insights into their function. Accurate identification of the interacting proteins in macromolecular complexes is easiest after purification to near homogeneity. To this end, the tandem affinity purification (TAP) system with subsequent protein identification by high-throughput mass spectrometry was developed (1, 2) to systematically characterize native protein complexes and transient protein interactions under near-physiological conditions. The TAP tag containing two adjacent affinity purification tags (calmodulin-binding peptide and Staphylococcus aureus protein A) separated by a tobacco etch virus (TEV) protease cleavage site is fused with the open reading frame of interest. Using homologous recombination, a fusion library was constructed for the yeast Saccharomyces cerevisiae (3) in which the carboxy-terminal end of each predicted open reading frame is individually tagged in the chromosome so that the resulting fusion proteins are expressed under the control of their natural promoters (3). In this chapter, an optimized protocol for systematic protein purification and subsequent mass spectrometry-based protein identification is described in detail for the protein complexes of S. cerevisiae (4-6).
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Affiliation(s)
- Mohan Babu
- Banting and Best Department of Medical Research, University of Toronto, Toronto, ON, Canada, M5S 3E1
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Zhao Y, Kurian D, Xu H, Petherbridge L, Smith LP, Hunt L, Nair V. Interaction of Marek's disease virus oncoprotein Meq with heat-shock protein 70 in lymphoid tumour cells. J Gen Virol 2009; 90:2201-8. [DOI: 10.1099/vir.0.012062-0] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
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Affiliation(s)
- Arthur Günzl
- Department of Genetics and Developmental Biology, University of Connecticut Health Center Farmington Connecticut
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Kremer H, Cremers FPM. Positional cloning of deafness genes. Methods Mol Biol 2009; 493:215-238. [PMID: 18839350 DOI: 10.1007/978-1-59745-523-7_13] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
The identification of the majority of the known causative genes involved in nonsyndromic sensorineural hearing loss (NSHL) started with linkage analysis as part of a positional cloning procedure. The human and mouse genome projects in combination with technical developments on genotyping, transcriptomics, proteomics, and the creation of animal models have greatly enhanced the speed of disease gene identification. In the present chapter, we first discuss the possibilities for exclusion of known NSHL loci and genes. Subsequently, methods are described to determine the genomic regions that contain the genetic defects. These include linkage analysis with genotyping and statistical evaluation and the determination of copy number variations. In the case of a large genomic region, candidate genes are selected and prioritized using gene expression analysis, protein network data, and phenotypes of animal models. A number of algorithms are described to automate the process of candidate gene selection. The novel high-throughput sequencing techniques might make gene selection and prioritization unnecessary in the near future. Once genetic variants are identified, questions on pathogenicity need to be addressed, which is the topic of the last section of this chapter.
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Affiliation(s)
- Hannie Kremer
- Department of Otorhinolaryngology, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
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A feedback loop comprising lin-28 and let-7 controls pre-let-7 maturation during neural stem-cell commitment. Nat Cell Biol 2008; 10:987-93. [PMID: 18604195 DOI: 10.1038/ncb1759] [Citation(s) in RCA: 629] [Impact Index Per Article: 39.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2008] [Accepted: 06/16/2008] [Indexed: 01/12/2023]
Abstract
miRNA populations, including mammalian homologues of lin-4 (mir-125) and let-7, undergo a marked transition during stem-cell differentiation. Originally identified on the basis of their mutational phenotypes in stem-cell maturation, mir-125 and let-7 are strongly induced during neural differentiation of embryonic stem (ES) cells and embryocarcinoma (EC) cells. We report that embryonic neural stem (NS) cells express let-7 and mir-125, and investigate post-transcriptional mechanisms contributing to the induction of let-7. We demonstrate that the pluripotency factor Lin-28 binds the pre-let-7 RNA and inhibits processing by the Dicer ribonuclease in ES and EC cells. In NS cells, Lin-28 is downregulated by mir-125 and let-7, allowing processing of pre-let-7 to proceed. Suppression of let-7 or mir-125 activity in NS cells led to upregulation of Lin-28 and loss of pre-let-7 processing activity, suggesting that let-7, mir-125 and lin-28 participate in an autoregulatory circuit that controls miRNA processing during NS-cell commitment.
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Pieroni E, de la Fuente van Bentem S, Mancosu G, Capobianco E, Hirt H, de la Fuente A. Protein networking: insights into global functional organization of proteomes. Proteomics 2008; 8:799-816. [PMID: 18297653 DOI: 10.1002/pmic.200700767] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The formulation of network models from global protein studies is essential to understand the functioning of organisms. Network models of the proteome enable the application of Complex Network Analysis, a quantitative framework to investigate large complex networks using techniques from graph theory, statistical physics, dynamical systems and other fields. This approach has provided many insights into the functional organization of the proteome so far and will likely continue to do so. Currently, several network concepts have emerged in the field of proteomics. It is important to highlight the differences between these concepts, since different representations allow different insights into functional organization. One such concept is the protein interaction network, which contains proteins as nodes and undirected edges representing the occurrence of binding in large-scale protein-protein interaction studies. A second concept is the protein-signaling network, in which the nodes correspond to levels of post-translationally modified forms of proteins and directed edges to causal effects through post-translational modification, such as phosphorylation. Several other network concepts were introduced for proteomics. Although all formulated as networks, the concepts represent widely different physical systems. Therefore caution should be taken when applying relevant topological analysis. We review recent literature formulating and analyzing such networks.
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Affiliation(s)
- Enrico Pieroni
- CRS4 Bioinformatica, c/o Parco Tecnologico POLARIS, Pula, Italy
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Tanaka Y, Bond MR, Kohler JJ. Photocrosslinkers illuminate interactions in living cells. MOLECULAR BIOSYSTEMS 2008; 4:473-80. [DOI: 10.1039/b803218a] [Citation(s) in RCA: 144] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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Hovhannisyan RH, Carstens RP. Heterogeneous ribonucleoprotein m is a splicing regulatory protein that can enhance or silence splicing of alternatively spliced exons. J Biol Chem 2007; 282:36265-74. [PMID: 17959601 DOI: 10.1074/jbc.m704188200] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Splicing of fibroblast growth factor receptor 2 (FGFR2) alternative exons IIIb and IIIc is regulated by the auxiliary RNA cis-element ISE/ISS-3 that promotes splicing of exon IIIb and silencing of exon IIIc. Using RNA affinity chromatography, we have identified heterogeneous nuclear ribonucleoprotein M (hnRNP M) as a splicing regulatory factor that binds to ISE/ISS-3 in a sequence-specific manner. Overexpression of hnRNP M promoted exon IIIc skipping in a cell line that normally includes it, and association of hnRNP M with ISE/ISS-3 was shown to contribute to this splicing regulatory function. Thus hnRNP M, along with other members of the hnRNP family of RNA-binding proteins, plays a combinatorial role in regulation of FGFR2 alternative splicing. We also determined that hnRNP M can affect the splicing of several other alternatively spliced exons. This activity of hnRNP M included the ability not only to induce exon skipping but also to promote exon inclusion. This is the first report demonstrating a role for this abundant hnRNP family member in alternative splicing in mammals and suggests that this protein may broadly contribute to the fidelity of splice site recognition and alternative splicing regulation.
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Affiliation(s)
- Ruben H Hovhannisyan
- Renal-Electrolyte and Hypertension Division, Department of Medicine, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104-4539, USA
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