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Strobel EJ, Lis JT, Lucks JB. Chemical roadblocking of DNA transcription for nascent RNA display. J Biol Chem 2020; 295:6401-6412. [PMID: 32209658 DOI: 10.1074/jbc.ra120.012641] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2020] [Revised: 03/20/2020] [Indexed: 11/06/2022] Open
Abstract
Site-specific arrest of RNA polymerases (RNAPs) is fundamental to several technologies that assess RNA structure and function. Current in vitro transcription "roadblocking" approaches inhibit transcription elongation by blocking RNAP with a protein bound to the DNA template. One limitation of protein-mediated transcription roadblocking is that it requires inclusion of a protein factor extrinsic to the minimal in vitro transcription reaction. In this work, we developed a chemical approach for halting transcription by Escherichia coli RNAP. We first established a sequence-independent method for site-specific incorporation of chemical lesions into dsDNA templates by sequential PCR and translesion synthesis. We then show that interrupting the transcribed DNA strand with an internal desthiobiotin-triethylene glycol modification or 1,N6-etheno-2'-deoxyadenosine base efficiently and stably halts Escherichia coli RNAP transcription. By encoding an intrinsic stall site within the template DNA, our chemical transcription roadblocking approach enables display of nascent RNA molecules from RNAP in a minimal in vitro transcription reaction.
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Affiliation(s)
- Eric J Strobel
- Department of Chemical and Biological Engineering, Northwestern University, Evanston, Illinois 60208 .,Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York 14850
| | - John T Lis
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York 14850
| | - Julius B Lucks
- Department of Chemical and Biological Engineering, Northwestern University, Evanston, Illinois 60208.,Center for Synthetic Biology, Northwestern University, Evanston, Illinois 60208
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Ngo C, Mehta R, Aggarwal K, Fikes AG, Santos IC, Greer SM, Que EL. Pull-Down of Metalloproteins in Their Native States by Using Desthiobiotin-Based Probes. Chembiochem 2019; 20:1003-1007. [PMID: 30520207 PMCID: PMC6530555 DOI: 10.1002/cbic.201800613] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2018] [Indexed: 11/07/2022]
Abstract
One-third of all proteins are estimated to require metals for structural stability and/or catalytic activity. Desthiobiotin probes containing metal binding groups can be used to capture metalloproteins with exposed active-site metals under mild conditions so as to prevent changes in metallation state. The proof-of-concept was demonstrated with carbonic anhydrase (CA), an open active site, Zn2+ -containing protein. CA was targeted by using sulfonamide derivatives. Linkers of various lengths and structures were screened to determine the optimal structure for capture of the native protein. The optimized probes could selectively pull down CA from red blood cell lysate and other protein mixtures. Pull-down of differently metallated CAs was also investigated.
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Affiliation(s)
- Chinh Ngo
- Department of Chemistry, University of Texas at Austin, 105 E 24 St Stop A5300, Austin, TX 78712, USA
| | - Radhika Mehta
- Department of Chemistry, University of Texas at Austin, 105 E 24 St Stop A5300, Austin, TX 78712, USA
| | - Kanchan Aggarwal
- Department of Chemistry, University of Texas at Austin, 105 E 24 St Stop A5300, Austin, TX 78712, USA
| | - Audrey G. Fikes
- Department of Chemistry, University of Texas at Austin, 105 E 24 St Stop A5300, Austin, TX 78712, USA
| | - Ines C. Santos
- Department of Chemistry, University of Texas at Austin, 105 E 24 St Stop A5300, Austin, TX 78712, USA
| | - Sylvester M. Greer
- Department of Chemistry, University of Texas at Austin, 105 E 24 St Stop A5300, Austin, TX 78712, USA
| | - Emily L. Que
- Department of Chemistry, University of Texas at Austin, 105 E 24 St Stop A5300, Austin, TX 78712, USA
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Panchapakesan SSS, Ferguson ML, Hayden EJ, Chen X, Hoskins AA, Unrau PJ. Ribonucleoprotein purification and characterization using RNA Mango. RNA 2017; 23:1592-1599. [PMID: 28747322 PMCID: PMC5602116 DOI: 10.1261/rna.062166.117] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/19/2017] [Accepted: 07/12/2017] [Indexed: 05/04/2023]
Abstract
The characterization of RNA-protein complexes (RNPs) is a difficult but increasingly important problem in modern biology. By combining the compact RNA Mango aptamer with a fluorogenic thiazole orange desthiobiotin (TO1-Dtb or TO3-Dtb) ligand, we have created an RNA tagging system that simplifies the purification and subsequent characterization of endogenous RNPs. Mango-tagged RNP complexes can be immobilized on a streptavidin solid support and recovered in their native state by the addition of free biotin. Furthermore, Mango-based RNP purification can be adapted to different scales of RNP isolation ranging from pull-down assays to the isolation of large amounts of biochemically defined cellular RNPs. We have incorporated the Mango aptamer into the S. cerevisiae U1 small nuclear RNA (snRNA), shown that the Mango-snRNA is functional in cells, and used the aptamer to pull down a U1 snRNA-associated protein. To demonstrate large-scale isolation of RNPs, we purified and characterized bacterial RNA polymerase holoenzyme (HE) in complex with a Mango-containing 6S RNA. We were able to use the combination of a red-shifted TO3-Dtb ligand and eGFP-tagged HE to follow the binding and release of the 6S RNA by two-color native gel analysis as well as by single-molecule fluorescence cross-correlation spectroscopy. Together these experiments demonstrate how the Mango aptamer in conjunction with simple derivatives of its flurophore ligands enables the purification and characterization of endogenous cellular RNPs in vitro.
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Affiliation(s)
- Shanker Shyam S Panchapakesan
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada
| | - Matthew L Ferguson
- Department of Physics, Boise State University, Boise, Idaho 83725, USA
- Department of Biological Science and Biomolecular Sciences Graduate Program, Boise State University, Boise, Idaho 83725, USA
| | - Eric J Hayden
- Department of Biological Science and Biomolecular Sciences Graduate Program, Boise State University, Boise, Idaho 83725, USA
| | - Xin Chen
- Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - Aaron A Hoskins
- Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - Peter J Unrau
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada
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Ahmad Hussin N, Pathirana RU, Hasim S, Tati S, Scheib-Owens JA, Nickerson KW. Biotin Auxotrophy and Biotin Enhanced Germ Tube Formation in Candida albicans. Microorganisms 2016; 4:E37. [PMID: 27681931 DOI: 10.3390/microorganisms4030037] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2016] [Revised: 09/07/2016] [Accepted: 09/14/2016] [Indexed: 11/17/2022] Open
Abstract
Due to the increased number of immunocompromised patients, infections with the pathogen Candida albicans have significantly increased in recent years. C. albicans transition from yeast to germ tubes is one of the essential factors for virulence. In this study we noted that Lee's medium, commonly used to induce filamentation, contained 500-fold more biotin than needed for growth and 40-fold more biotin than is typically added to growth media. Thus, we investigated the effects of excess biotin on growth rate and filamentation by C. albicans in different media. At 37 °C, excess biotin (4 µM) enhanced germ tube formation (GTF) ca. 10-fold in both Lee's medium and a defined glucose-proline medium, and ca. 4-fold in 1% serum. Two biotin precursors, desthiobiotin and 7-keto-8-aminopelargonic acid (KAPA), also stimulated GTF. During these studies we also noted an inverse correlation between the number of times the inoculum had been washed and the concentration of serum needed to stimulate GTF. C. albicans cells that had been washed eight times achieved 80% GTF with only 0.1% sheep serum. The mechanism by which 1-4 µM biotin enhances GTF is still unknown except to note that equivalent levels of biotin are needed to create an internal supply of stored biotin and biotinylated histones. Biotin did not restore filamentation for any of the four known filamentation defective mutants tested. C. albicans is auxotrophic for biotin and this biotin auxotrophy was fulfilled by biotin, desthiobiotin, or KAPA. However, biotin auxotrophy is not temperature dependent or influenced by the presence of 5% CO₂. Biotin starvation upregulated the biotin biosynthetic genes BIO2, BIO3, and BIO4 by 11-, 1500-, and 150-fold, respectively, and BIO2p is predicted to be mitochondrion-localized. Based on our findings, we suggest that biotin has two roles in the physiology of C. albicans, one as an enzymatic cofactor and another as a morphological regulator. Finally, we found no evidence supporting prior claims that C. albicans only forms hyphae at very low biotin (0.1 nM) growth conditions.
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Ansari A, Patel R, Schultheis K, Naumovski V, Imoukhuede PI. A Method of Targeted Cell Isolation via Glass Surface Functionalization. J Vis Exp 2016:54315. [PMID: 27684992 PMCID: PMC5092063 DOI: 10.3791/54315] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
One of the limiting factors to the adoption and advancement of personalized medicine is the inability to develop diagnostic tools to probe individual nuances in expression from patient to patient. Current methodologies that try to separate cells to fill this niche result in disruption of physiological expression, making the separation technique useless as a diagnostic tool. In this protocol, we describe the functionalization and optimization of a surface for the cellular capture and release. This functionalized surface integrates biotinylated antibodies with a glass surface functionalized with an aminosilane (APTES), desthiobiotin and streptavidin. Cell release is facilitated through the introduction of biotin, allowing the recollection and purification of cells captured by the surface. This release is done through the targeting of the secondary moiety desthiobiotin, which results in a much more gentle release paradigm. This reduction in harsh reagents and shear forces reduces changes in cellular expression. The functionalized surface captures up to 80% of cells in a single cell mixture and has demonstrated 50% capture in a dual-cell mixture. Applications of this technology to xenografts and cancer separation studies are investigated. Quantification techniques for surface verification such as plate reader and ImageJ analyses are described as well.
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Affiliation(s)
- Ali Ansari
- Department of Bioengineering, University of Illinois at Urbana-Champaign
| | - Reema Patel
- Department of Liberal Arts & Sciences, University of Illinois at Urbana-Champaign
| | - Kinsey Schultheis
- Department of Bioengineering, University of Illinois at Urbana-Champaign
| | - Vesna Naumovski
- Department of Biomedical Engineering, Illinois Institute of Technology
| | - P I Imoukhuede
- Department of Bioengineering, University of Illinois at Urbana-Champaign;
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Ansari A, Lee-Montiel FT, Amos JR, Imoukhuede PI. Secondary anchor targeted cell release. Biotechnol Bioeng 2015; 112:2214-27. [PMID: 26010879 DOI: 10.1002/bit.25648] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2014] [Accepted: 05/11/2015] [Indexed: 01/11/2023]
Abstract
Personalized medicine offers the promise of tailoring therapy to patients, based on their cellular biomarkers. To achieve this goal, cellular profiling systems are needed that can quickly and efficiently isolate specific cell types without disrupting cellular biomarkers. Here we describe the development of a unique platform that facilitates gentle cell capture via a secondary, surface-anchoring moiety, and cell release. The cellular capture system consists of a glass surface functionalized with APTES, d-desthiobiotin, and streptavidin. Biotinylated mCD11b and hIgG antibodies are used to capture mouse macrophages (RAW 264.7) and human breast cancer (MCF7-GFP) cell lines, respectively. The surface functionalization is optimized by altering assay components, such as streptavidin, d-desthiobiotin, and APTES, to achieve cell capture on 80% of the functionalized surface and cell release upon biotin treatment. We also demonstrate an ability to capture 50% of target cells within a dual-cell mixture. This engineering advancement is a critical step towards achieving cell isolation platforms for personalized medicine.
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Affiliation(s)
| | | | - Jennifer R Amos
- Department of Bioengineering, University of Illinois at Urbana Champaign, Urbana, Illinois, 61801
| | - P I Imoukhuede
- Department of Bioengineering, University of Illinois at Urbana Champaign, Urbana, Illinois, 61801.
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Lu WC, Levy M, Kincaid R, Ellington AD. Directed evolution of the substrate specificity of biotin ligase. Biotechnol Bioeng 2014; 111:1071-81. [PMID: 24375025 DOI: 10.1002/bit.25176] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2013] [Revised: 11/22/2013] [Accepted: 12/16/2013] [Indexed: 11/08/2022]
Abstract
We have developed selection scheme for directing the evolution of Escherichia coli biotin protein ligase (BPL) via in vitro compartmentalization, and have used this scheme to alter the substrate specificity of the ligase towards the utilization of the biotin analogue desthiobiotin. In this scheme, a peptide substrate (BAP) was conjugated to a DNA library encoding BirA, emulsified such that there was a single template per compartment, and protein variants were transcribed and translated in vitro. Those variants that could efficiently desthiobiotinylate their corresponding peptide:DNA conjugate were subsequently captured and amplified. Following just six rounds of selection and amplification several variants that demonstrated higher activity with desthiobiotin were identified. The best variants from Round 6, BirA6-40 and BirA6-47 , showed 17-fold and 10-fold higher activity, respectively, their abilities to use desthiobiotin as a substrate. While selected enzymes contained a number of substitutions, a single mutation, M157T, proved sufficient to provide much greater activity with desthiobiotin. Further characterization of BirA6-40 and the single substitution variant BirAM157T revealed that they had twoto threefold higher kcat values for desthiobiotin. These variants had also lost much of their ability to utilize biotin, resulting in orthogonal enzymes that in conjunction with streptavidin variants that can utilize desthiobiotin may prove to be of great use in developing additional, robust conjugation handles for a variety of biological and biotechnological applications.
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Affiliation(s)
- Wei-Cheng Lu
- Institute of Cellular and Molecular Biology, University of Texas at Austin, Austin, Texas
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Abstract
The fatty acid composition of animal cells cultured in serum-free medium can be manipulated when the synthesis of endogenous fatty acids is inhibited by a biotin analog and fatty acids are supplied in the medium as detergent esters of Tween. When mouse LM cells were grown in medium supplemented with Tween-19:0 (an ester of Tween and nonadecanoic acid), odd chain fatty acid content of cellular phospholipids and neutral lipids increased from 1% to 75%. Concurrently, the saturated fatty acid content increased from 27% to 85%. Similar alterations in fatty acid content have been observed when BHK(21) cells are subjected to the same enrichment regime. The ability to control the fatty acid composition of cultured animal cells is a prerequisite to investigations into the role of the membrane lipid physical state in processes unique to these cells.
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