scholarly journals Synthetic logic circuits using RNA aptamer against T7 RNA polymerase

2014 ◽  
Author(s):  
Jongmin Kim ◽  
Juan F Quijano ◽  
Enoch Yeung ◽  
Richard M Murray
Keyword(s):  
Rna Polymerase ◽  
Expression System ◽  
Building Blocks ◽  
Logic Circuits ◽  
T7 Rna Polymerase ◽  
Free Expression ◽  
Rna Aptamer ◽  
Cell Free Expression System

Recent advances in nucleic acids engineering introduced several RNA-based regulatory components for synthetic gene circuits, expanding the toolsets to engineer organisms. In this work, we designed genetic circuits implementing an RNA aptamer previously described to have the capability of binding to the T7 RNA polymerase and inhibiting its activity in vitro. Using in vitro transcription assays, we first demonstrated the utility of the RNA aptamer in combination with programmable synthetic transcription networks. As a step to quickly assess the feasibility of aptamer functions in vivo, a cell-free expression system was used as a breadboard to emulate the in vivo conditions of E. coli. We tested the aptamer and its three sequence variants in the cell-free expression system, verifying the aptamer functionality in the cell-free testbed. In vivo expression of aptamer and its variants demonstrated control over GFP expression driven by T7 RNA polymerase with different response curves, indicating its ability to serve as building blocks for both logic circuits and transcriptional cascades. This work elucidates the potential of RNA-based regulators for cell programming with improved controllability leveraging the fast production and degradation time scales of RNA molecules.

scholarly journals Engineering efficient termination of bacteriophage T7 RNA polymerase transcription

2021 ◽  
Author(s):  
Diana Gabriela Calvopina Chavez ◽  
Mikaela Anne Gardner ◽  
Joel S Griffitts
Keyword(s):  
Rna Polymerase ◽  
Molecular Level ◽  
Expression System ◽  
T7 Rna Polymerase ◽  
Bacteriophage T7 ◽  
Lower Efficiency ◽  
Transcriptional Termination ◽  
T7 Polymerase

The bacteriophage T7 expression system is one of the most prominent transcription systems used in biotechnology and molecular-level research. However, T7 RNA polymerase is prone to read-through transcription due to its high processivity. As a consequence, enforcing efficient transcriptional termination is difficult. The termination hairpin found natively in the T7 genome is adapted to be inefficient, exhibiting 62% termination efficiency in vivo and even lower efficiency in vitro. In this study, we engineered a series of sequences that outperform the efficiency of the native terminator hairpin. By embedding a previously discovered 8-nucleotide T7 polymerase pause sequence within a synthetic hairpin sequence, we observed in vivo termination efficiency of 91%; by joining two short sequences into a tandem 2-hairpin structure, termination efficiency was increased to 98% in vivo and 91% in vitro. This study also tests the ability of these engineered sequences to terminate transcription of the Escherichia coli RNA polymerase. Two out of three of the most successful T7 polymerase terminators also facilitated termination of the bacterial polymerase with around 99% efficiency.

scholarly journals Protein degradation in a TX-TL cell-free expression system using ClpXP protease

2015 ◽  
Author(s):  
Zachary Sun ◽  
Jongmin Kim ◽  
Vipul Singhal ◽  
Richard M Murray
Keyword(s):  
Protein Degradation ◽  
Expression System ◽  
Free Expression ◽  
Batch Mode ◽  
Protein Targets ◽  
Resource Limited ◽  
Escherichia Coli Expression ◽  
Cell Free Expression System

An in vitro S30-based Escherichia coli expression system (“Transcription-Translation”, or “TX-TL”) has been developed as an alternative prototyping environment to the cell for synthetic circuits [1-5]. Basic circuit elements, such as switches and cascades, have been shown to function in TX-TL, as well as bacteriophage assembly [2, 6]. Circuits can also be prototyped from basic parts within 8 hours, avoiding cloning and transformation steps [7]. However, most published results have been obtained in a “batch mode” reaction, where factors that play an important role for in vivo circuit dynamics – namely protein degradation and protein dilution – are severely hindered or are not present. This limits the complexity of circuits built in TX-TL without steady-state or continuous-flow solutions [8-10]. However, alternate methods that enable dilution either require extra equipment and expertise or demand lower reaction throughput. We explored the possibility of supplementing TX-TL with ClpXP, an AAA+ protease pair that selectively degrades tagged proteins [11], to provide finely-tuned degradation. The mechanism of ClpXP degradation has been extensively studied both in vitro and in vivo [12-15]. However, it has not been characterized for use in synthetic circuits – metrics such as toxicity, ATP usage, degradation variation over time, and cellular loading need to be determined. In particular, TX-TL in batch mode is known to be resource limited [16], and ClpXP is known to require significant amounts of ATP to unfold different protein targets [17, 18]. We find that ClpXP’s protein degradation dynamics is dependent on protein identity, but can be determined experimentally. Degradation follows Michaels-Menten kinetics, and can be fine tuned by ClpX or ClpP concentration. Added purified ClpX is also not toxic to TX-TL reactions. Therefore, ClpXP provides a controllable way to introduce protein degradation and dynamics into synthetic circuits in TX-TL.

scholarly journals Incompatibility of DFHBI based fluorescent RNA aptamers with particular commercial cell-free expression systems

2021 ◽  
Author(s):  
Alexander J Speakman ◽  
Katherine E Dunn
Keyword(s):  
Expression System ◽  
In Vitro Transcription ◽  
Rna Aptamers ◽  
Free Expression ◽  
Reaction Products ◽  
Expression Systems ◽  
E Coli ◽  
Cell Free Expression System

Fluorescent RNA aptamers are an increasingly used tool for quantifying transcription and for visualising RNA interactions, both in vitro and in vivo. However when tested in the commercially available, E. coli extract based Expressway™ cell-free expression system, no fluorescence is detected. The same experimental setup is shown to successfully produce fluorescent RNA aptamers when tested in another buffer designed for in vitro transcription, and RNA purification of the Expressway™ reaction products show that transcription does occur, but does not result in a fluorescent product. In this paper we demonstrate the incompatibility of a narrow selection of RNA aptamers in one particular cell-free expression system, and consider that similar issues may arise with other cell-free expression systems, RNA aptamers, and their corresponding fluorophores.

scholarly journals Efficacy of a Potential Trivalent Vaccine Based on Hc Fragments of Botulinum Toxins A, B, and E Produced in a Cell-Free Expression System

2010 ◽  
Vol 17 (5) ◽  
pp. 784-792 ◽  
Author(s):  
R. Zichel ◽  
A. Mimran ◽  
A. Keren ◽  
A. Barnea ◽  
I. Steinberger-Levy ◽  
...  
Keyword(s):  
Expression System ◽  
Free Expression ◽  
Enzyme Linked Immunosorbent Assay ◽  
High Dose ◽  
Botulinum Toxins ◽  
Free System ◽  
Toxin Complex ◽  
A Cell ◽  
Cell Free Expression System

ABSTRACT Botulinum toxins produced by the anaerobic bacterium Clostridium botulinum are the most potent biological toxins in nature. Traditionally, people at risk are immunized with a formaldehyde-inactivated toxin complex. Second generation vaccines are based on the recombinant carboxy-terminal heavy-chain (Hc) fragment of the neurotoxin. However, the materialization of this approach is challenging, mainly due to the high AT content of clostridial genes. Herein, we present an alternative strategy in which the native genes encoding Hc proteins of botulinum toxins A, B, and E were used to express the recombinant Hc fragments in a cell-free expression system. We used the unique property of this open system to introduce different combinations of chaperone systems, protein disulfide isomerase (PDI), and reducing/oxidizing environments directly to the expression reaction. Optimized expression conditions led to increased production of soluble Hc protein, which was successfully scaled up using a continuous exchange (CE) cell-free system. Hc proteins were produced at a concentration of more than 1 mg/ml and purified by one-step Ni+ affinity chromatography. Mice immunized with three injections containing 5 μg of any of the in vitro-expressed, alum-absorbed, Hc vaccines generated a serum enzyme-linked immunosorbent assay (ELISA) titer of 105 against the native toxin complex, which enabled protection against a high-dose toxin challenge (103 to 106 mouse 50% lethal dose [MsLD50]). Finally, immunization with a trivalent HcA, HcB, and HcE vaccine protected mice against the corresponding trivalent 105 MsLD50 toxin challenge. Our results together with the latest developments in scalability of the in vitro protein expression systems offer alternative routes for the preparation of botulinum vaccine.

scholarly journals Revisiting T7 RNA polymerase transcription in vitro with the Broccoli RNA aptamer as a simplified real-time fluorescent reporter

2020 ◽  
pp. jbc.RA120.014553
Author(s):  
Zachary J Kartje ◽  
Helen I Janis ◽  
Shaoni Mukhopadhyay ◽  
Keith T Gagnon
Keyword(s):  
Rna Polymerase ◽  
Real Time ◽  
High Throughput Screening ◽  
In Vitro Transcription ◽  
T7 Rna Polymerase ◽  
Rna Aptamer ◽  
Reaction Conditions ◽  
Fluorescent Reporter ◽  
Transcription In Vitro

Methods for rapid and high-throughput screening of transcription in vitro to examine reaction conditions, enzyme mutants, promoter variants, and small molecule modulators can be extremely valuable tools. However, these techniques may be difficult to establish or inaccessible to many researchers. To develop a straightforward and cost-effective platform for assessing transcription in vitro, we used the “Broccoli” RNA aptamer as a direct, real-time fluorescent transcript readout. To demonstrate the utility of our approach, we screened the effect of common reaction conditions and components on bacteriophage T7 RNA polymerase (RNAP) activity using a common quantitative PCR instrument for fluorescence detection. Several essential conditions for in vitro transcription by T7 RNAP were confirmed with this assay, including the importance of enzyme and substrate concentrations, co-variation of magnesium and nucleoside triphosphates, and the effects of several typical additives. When we used this method to assess all possible point mutants of a canonical T7 RNAP promoter, our results coincided well with previous reports. This approach should translate well to a broad variety of bacteriophage in vitro transcription systems and provides a platform for developing fluorescence-based readouts of more complex transcription systems in vitro.

In vivo and in vitro activities of point mutants of the bacteriophage T7 RNA polymerase promoter

Biochemistry ◽  
1992 ◽  
Vol 31 (37) ◽  
pp. 9073-9080 ◽  
Author(s):  
Richard A. Ikeda ◽  
G. Sakuntala Warshamana ◽  
Lisa L. Chang
Keyword(s):  
Rna Polymerase ◽  
T7 Rna Polymerase ◽  
Bacteriophage T7 ◽  
Rna Polymerase Promoter

Directed Evolution of a Panel of Orthogonal T7 RNA Polymerase Variants for in Vivo or in Vitro Synthetic Circuitry

2014 ◽  
Vol 4 (10) ◽  
pp. 1070-1076 ◽  
Author(s):  
Adam J. Meyer ◽  
Jared W. Ellefson ◽  
Andrew D. Ellington
Keyword(s):  
Rna Polymerase ◽  
Directed Evolution ◽  
T7 Rna Polymerase

scholarly journals In vivo and in vitro transcription of T7 early genes by T7 RNA polymerase

FEBS Letters ◽  
1973 ◽  
Vol 33 (3) ◽  
pp. 335-338 ◽  
Author(s):  
J.R. Lillehaug ◽  
D. Helland ◽  
N.O. Sjöberg
Keyword(s):  
Rna Polymerase ◽  
In Vitro Transcription ◽  
T7 Rna Polymerase ◽  
Early Genes

scholarly journals A Methylation-Directed, Synthetic Pap Switch Based on Self-Complementary Regulatory DNA in an All-E. Coli Cell-Free Expression System

2020 ◽  
Author(s):  
Emanuel Worst ◽  
oemer Kurt ◽  
Marc Finkler ◽  
Marc Schenkelberger ◽  
Vincent Noireaux ◽  
...  
Keyword(s):  
Expression System ◽  
Regulatory Region ◽  
Phase Variation ◽  
Coli Strain ◽  
Coli Cell ◽  
Free Expression ◽  
E Coli ◽  
Regulatory Dna ◽  
Cell Free Expression System

<p>Pyelonephritis-associated pili (pap) enable migration of the uropathogenic Escherichia coli strain (UPEC) through the urinary tract. UPEC can switch between a stable 'ON phase' where the corresponding pap genes are expressed and a stable 'OFF phase' where their transcription is repressed. Hereditary, alternate DNA methylation of only two GATC motives within the regulatory region stabilizes the respective phase over many generations. The underlying molecular mechanism is only partly understood. Previous investigations suggest that in vivo phase-variation stability results from cooperative action of the transcriptional regulators Lrp and PapI. Here, we use an E. coli cell-free expression system to study the function of pap regulatory region based on a specially designed, synthetic construct flanked by two reporter genes encoding fluorescent proteins for simple readout. Based on our observations we suggest that Lrp and the conformation of the self-complementary regulatory DNA play a strong role in the regulation of phase-variation. Our work not only contributes to better understand the phase variation mechanism, but it represents a successful start for engineering stable, hereditary and strong expression control based on methylation.</p>

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