SynBioFromLeukipposInstitute

How anti-CRISPR proteins and other molecules could bolster biosecurity and improve medical treatments.

All viruses require strategies to inhibit or evade the immune pathways of cells that they infect. The viruses that infect bacteria, bacteriophages (phages), must avoid immune pathways that target nucleic acids, such as CRISPR–Cas and restriction-modification systems, to replicate efficiently1. Here we show that jumbo phage ΦKZ segregates its DNA from immunity nucleases of its host, Pseudomonas aeruginosa, by constructing a proteinaceous nucleus-like compartment. ΦKZ is resistant to many immunity mechanisms that target DNA in vivo, including two subtypes of CRISPR–Cas3, Cas9, Cas12a and the restriction enzymes HsdRMS and EcoRI. Cas proteins and restriction enzymes are unable to access the phage DNA throughout the infection, but engineering the relocalization of EcoRI inside the compartment enables targeting of the phage and protection of host cells. Moreover, ΦKZ is sensitive to Cas13a—a CRISPR–Cas enzyme that targets RNA—probably owing to phage mRNA localizing to the cytoplasm. Collectively, we propose that Pseudomonas jumbo phages evade a broad spectrum of DNA-targeting nucleases through the assembly of a protein barrier around their genome. The jumbo phage ΦKZ constructs a proteinaceous nucleus-like compartment around its genome that protects phage DNA from degradation by DNA-targeting immune effectors of the host, including CRISPR–Cas and restriction enzymes.

Genome-scale engineering is an indispensable tool to understand genome functions due to our limited knowledge of cellular networks. Unfortunately, most existing methods for genome-wide genotype–phenotype mapping are limited to a single mode of genomic alteration, i.e. overexpression, repression, or deletion. Here we report a multi-functional genome-wide CRISPR (MAGIC) system to precisely control the expression level of defined genes to desired levels throughout the whole genome. By combining the tri-functional CRISPR system and array-synthesized oligo pools, MAGIC is used to create, to the best of our knowledge, one of the most comprehensive and diversified genomic libraries in yeast ever reported. The power of MAGIC is demonstrated by the identification of previously uncharacterized genetic determinants of complex phenotypes, particularly those having synergistic interactions when perturbed to different expression levels. MAGIC represents a powerful synthetic biology tool to investigate fundamental biological questions as well as engineer complex phenotypes for biotechnological applications. Genome-scale engineering is generally limited to single methods of alteration such as overexpression, repression or deletion. Here the authors present a tri-functional CRISPR system that can engineer complex synergistic interactions in a genome-wide manner.

Augmenting live cells with new signal transduction capabilities is a key objective in genetic engineering and synthetic biology. We showed earlier that two-component signaling pathways could function in mammalian cells, albeit while losing their ligand sensitivity. Here, we show how to transduce small-molecule ligands in a dose-dependent fashion into gene expression in mammalian cells using two-component signaling machinery. First, we engineer mutually complementing truncated mutants of a histidine kinase unable to dimerize and phosphorylate the response regulator. Next, we fuse these mutants to protein domains capable of ligand-induced dimerization, which restores the phosphoryl transfer in a ligand-dependent manner. Cytoplasmic ligands are transduced by facilitating mutant dimerization in the cytoplasm, while extracellular ligands trigger dimerization at the inner side of a plasma membrane. These findings point to the potential of two-component regulatory systems as enabling tools for orthogonal signaling pathways in mammalian cells. Bacterial two-component signaling machinery has been reprogrammed for orthogonal signaling in mammalian cells that is triggered by small-molecule-mediated dimerization or ligand-induced GPCR/β-arrestin signaling.

Abstract. Allosteric transcription factors (aTFs) have proven widely applicable for biotechnology and synthetic biology as ligand-specific biosensors enabling

The lack of available genetic modules is a fundamental issue in mammalian synthetic biology. Especially, the variety of genetic parts for translational control are limited. Here we report a new set of synthetic mRNA-based translational switches by engineering RNA-binding proteins (RBPs) and RBP-binding RNA motifs (aptamers) that perform strong translational repression. We redesigned the RNA motifs with RNA scaffolds and improved the efficiency of the repression to target RBPs. Using new and previously reported mRNA switches, we demonstrated that the orthogonality of translational regulation was ensured among five different RBP-responsive switches. Moreover, the new switches functioned not only with plasmid introduction, but also with RNA-only delivery, which provides a transient and safer regulation of expression. The translational regulators using RNA-protein interactions provide an alternative strategy to construct complex genetic circuits for future cell engineering and therapeutics.

CRISPR/Cas technology can do more than alter genes. A research team at the University of Freiburg is using what are known as gene scissors—which scientists can use to edit genetic material—in order to better diagnose diseases such as cancer. In a study, the researchers introduce a microfluidic chip which recognizes small fragments of RNA, indicating a specific type of cancer more rapidly and precisely than the techniques available up to now. The results are recently published in the scientific journal Advanced Materials.

Molecular switches that change their conformation upon target binding offer powerful capabilities for biotechnology and synthetic biology. Aptamers are useful as molecular switches because they offer excellent binding properties, undergo reversible folding, and can be engineered into many nanostructures. Unfortunately, the thermodynamic and kinetic properties of the aptamer switches developed to date are intrinsically coupled, such that high temporal resolution can only be achieved at the cost of lower sensitivity or high background. Here, we describe a design strategy that decouples and enables independent control over the thermodynamics and kinetics of aptamer switches. Starting from a single aptamer, we create an array of aptamer switches with effective dissociation constants ranging from 10 μM to 40 mM and binding kinetics ranging from 170 ms to 3 s. Our strategy is broadly applicable to other aptamers, enabling the development of switches suitable for a diverse range of biotechnology applications. Aptamer switches are promising biotechnological tools but coupling of their affinity and temporal response limits their versatility. Here, the authors developed an intramolecular strand-displacement strategy that allows for independent fine-tuning of thermodynamics and kinetics of aptamer switches.

Programming cells to sense multiple‐inputs and activate cellular signal transduction cascades is of great interest. Albeit it has been achieved via engineering of genetic circuits using syntheti

Cell‐based biosensors offer cheap, portable and simple methods of detecting molecules of interest but have yet to be truly adopted commercially. Issues with their performance and specificit

As the first clinical-trial results trickle in, researchers look ahead to more sophisticated medical applications for genome editing.

Protein interactions guide most cellular processes. Orthogonal hetero-specific protein–protein interaction domains may facilitate better control of engineered biological systems. Here, we report a tunable de novo designed set of orthogonal coiled-coil (CC) peptide heterodimers (called the NICP set) and its application for the regulation of diverse cellular processes, from cellular localization to transcriptional regulation. We demonstrate the application of CC pairs for multiplex localization in single cells and exploit the interaction strength and variable stoichiometry of CC peptides for tuning of gene transcription strength. A concatenated CC peptide tag (CCC-tag) was used to construct highly potent CRISPR–dCas9-based transcriptional activators and to amplify the response of light and small molecule-inducible transcription in cell culture as well as in vivo. The NICP set and its implementations represent a valuable toolbox of minimally disruptive modules for the recruitment of versatile functional domains and regulation of cellular processes for synthetic biology. A set of orthogonal coiled-coil peptide heterodimers were developed to enable control of protein localization as well as transcriptional regulation by enhancing effector recruitment to TALE and CRISPR–dCas9 systems in mammalian cells and in vivo.

Modularity has been the subject of intense investigation in systems biology for more than two decades. Whether modularity holds in biological networks…

Thanks to the synthetic biology, the laborious and restrictive procedure for producing a target protein in living microorganisms by biotechnological approaches can now experience a robust, plian

The field of basal cognition seeks to understand how adaptive, context-specific behavior occurs in non-neural biological systems. Embryogenesis and regeneration require plasticity in many tissue types to achieve structural and functional goals in diverse circumstances. Thus, advances in both evolutionary cell biology and regenerative medicine require an understanding of how non-neural tissues could process information. Neurons evolved from ancient cell types that used bioelectric signaling to perform computation. However, it has not been shown whether or how non-neural bioelectric cell networks can support computation. We generalize connectionist methods to non-neural tissue architectures, showing that a minimal non-neural Bio-Electric Network (BEN) model that utilizes the general principles of bioelectricity (electrodiffusion and gating) can compute. We characterize BEN behaviors ranging from elementary logic gates to pattern detectors, using both fixed and transient inputs to recapitulate various biological scenarios. We characterize the mechanisms of such networks using dynamical-systems and information-theory tools, demonstrating that logic can manifest in bidirectional, continuous, and relatively slow bioelectrical systems, complementing conventional neural-centric architectures. Our results reveal a variety of non-neural decision-making processes as manifestations of general cellular biophysical mechanisms and suggest novel bioengineering approaches to construct functional tissues for regenerative medicine and synthetic biology as well as new machine learning architectures.

The field of synthetic biology has used the engineered assembly of synthetic gene networks to create a wide range of functions in biological systems. To date, gene-circuit-based sensors have primarily used optical proteins (for example, fluorescent, colorimetric) as reporter outputs, which has limited the potential to measure multiple distinct signals. Here we present an electrochemical interface that permits expanded multiplexed reporting for cell-free gene-circuit-based sensors. We have engineered a scalable system of reporter enzymes that cleave specific DNA sequences in solution, which results in an electrochemical signal when these newly liberated strands are captured at the surface of a nanostructured microelectrode. We describe the development of this interface and show its utility using a ligand-inducible gene circuit and toehold switch-based sensors by demonstrating the detection of multiple antibiotic resistance genes in parallel. This technology has the potential to expand the field of synthetic biology by providing an interface for materials, hardware and software. Gene-circuit-based sensors have, to date, largely relied on optical proteins (such as green fluorescent protein) to report the output, which limits the signalling bandwidth. Now, an electrochemical output has been developed and integrated with cell-free gene circuits. This approach enables multiplexing of sensors and introduces the possibility of electronic-based logic, memory and response elements to synthetic biology.

Scientists at the University of Toronto (U of T) and Arizona State University (ASU) have developed the first direct gene circuit to electrode interface by combining cell-free synthetic biology with state-of-the-art nanostructured electrodes.

Synthetic biology uses living cells as the substrate for performing human-defined computations. Many current implementations of cellular computing are based on the “genetic circuit” metaphor, an approximation of the operation of silicon-based computers. Although this conceptual mapping has been relatively successful, we argue that it fundamentally limits the types of computation that may be engineered inside the cell, and fails to exploit the rich and diverse functionality available in natural living systems. We propose the notion of “cellular supremacy” to focus attention on domains in which biocomputing might offer superior performance over traditional computers. We consider potential pathways toward cellular supremacy, and suggest application areas in which it may be found. Synthetic biology uses cells as its computing substrate, often based on the genetic circuit concept. In this Perspective, the authors argue that existing synthetic biology approaches based on classical models of computation limit the potential of biocomputing, and propose that living organisms have under-exploited capabilities.

Many of the world's most common or deadly human pathogens are RNA-based viruses—Ebola, Zika and flu, for example—and most have no FDA-approved treatments. A team led by researchers at the Broad Institute of MIT and Harvard has now turned a CRISPR RNA-cutting enzyme into an antiviral that can be programmed to detect and destroy RNA-based viruses in human cells.