Molecular engineering articles within Nature Communications

Nucleic acid sensing involving CRISPR technologies is powerful but has certain limitations, such as PAM sequence requirements and limited multiplexing. Here, authors report a CRISPR-based barcoding technology which enables multiple outputs from any target sequence, based on cis- and trans-cleavage.

There is a low efficiency of A-to-G base conversion in at specific positions using base editors. Here the authors fuse ABE8e with the Rad51 DNA-binding domain to generate a hyperactive ABE allowing improved A-to-G editing efficiency at the region proximal to the PAM and improved simultaneous A/C conversion efficiency.

While the ribosome has been harnessed for synthetic biology, designing ribosomes has remained challenging. Here, the authors demonstrate a community science approach for rational design of ribosomes with beneficial properties.

There is a need to improve and expand mitochondrial base editing tools. Here the authors identify a DddA homolog from Simiaoa sunii (Ddd_Ss) which can efficiently deaminate cytosine in dsDNA; they develop cytosine base editors and introduce mutations at multiple mitochondrial DNA loci.

The treatment of snakebite envenoming is currently suboptimal. Existing antivenoms often lack efficacy and may cause adverse reactions. Here, the authors derive, develop, and demonstrate the utility of toxin-specific broadly-neutralizing human monoclonal antibodies with established reactivity across related venom toxins from different snake species and show efficacy in rodent models.

Genome editing in bacteria normally requires efficient recombination and high transformation efficiencies, which often isn’t. Here the authors report that systematically attenuating DNA targeting activity enables RecA-mediated repair in different bacteria, allowing chromosomal cleavage to drive editing.

The currently available transgenic T cell receptor (TCR) models represent high affinity antigen-TCR interactions. Authors here present an alternative approach to target an exogenous TCR into the physiological Trac locus in the germline of mice, which uncovers that the natural genomic context for TCRs can enhance the antigen sensitivity of lower affinity TCRs and enables the physiologic range of antigen-TCR interaction and a gene dosage dependent mechanism of central tolerance.

RNA provides a unique readout of a cell’s identity, physiologic status, and phenotype. Here the authors deliver an RNA sensing system that can use the information contained within cellular RNA to selectively control the activity of genetic programs.

Antigen display on outer membrane vesicles (OMVs) can be difficult to control and highly variable. Here, the authors describe a universal approach called AvidVax for linking biotinylated antigens to the exterior of OMVs and enabling rapid vaccine assembly.

Properties of cytidine and adenosine deaminases lead to off-target effects for cytosine base editors (CBEs) and adenine base editors (ABEs). Here the authors report that 25 TadA orthologs could be engineered to generate functional ABEs, CBEs or ACBEs via single/double mutations with minimised off-targets.

Hypercompact CRISPR-Cas12f systems have been engineered to generate miniABEs but these have limitations. Here the authors generate Cas12f-derived miniCBEs and develop miniABEs with improved editing and targeting scopes; they use these to correct pathogenic mutations in cell lines and introduce mutations in vivo.

CRISPR/Cas9-based homing gene drives have emerged as a potential new approach to mosquito control. Here the authors use transgenic lines with germline-specific regulatory elements to express Cas9 and achieve up to 94% inheritance bias, closing the gap between A. aegyptidrives and the highly efficient drives observed in Anopheles species.

CRISPR-based gene-drives can carry the Cas9 and guide RNA (gRNA) components in a single-linked cassette or in separate elements inserted into different genomic loci. Here the authors genetically transform and compare full versus split drives, with the former performing less efficiently than predicted.

Aromatic amino acids in proteins support ligand binding and protein stability. To parse the physiocochemical roles of aromatic interactions, here Galles, Infield and co-authors identify pyrrolysine-based aminoacyl-tRNA synthetases that enable the encoding of fluorinated phenylalanine amino acids.

Imaging non-repetitive loci in living cells remains challenging. Here, the authors engineered an inducible system whereby biomolecular assemblies can be guided to specific genomic loci by a nuclease-defective Cas9, allowing the simultaneous imaging and manipulation of the loci.

Antibiotic and anti-cancer therapy are challenged by mutation-mediated treatment resistance despite many mutations being maladaptive. Here, the authors introduce a system that shows how the probability of the long-term persistence of drug-resistant mutant lineages can be increased in dense microbial populations by acquiring multiple mutations.

The development of broad-spectrum antivirals is an important part of pandemic preparedness and response. Here the authors present ALICE, synthetic biology designer immune-like cells that act as a sense-and-destroy antiviral system can detect viruses from seven different genera, mimicking the human innate immune system.

Identifying the designers of engineered biological sequences would help promote biotechnological innovation while holding designers accountable. Here the authors present the winners of a 2020 data-science competition which improved on previous attempts to attribute plasmid sequences.

Gene activation methods are valuable for studying gene functions and may have potential applications in bioengineering and medicine. Here the authors developed Narta technology to achieve gene activation by recruiting artificial transcription factors to transcription sites through nascent RNAs of the target gene.

Engineering enzymes to accept noncanonical cofactor biomimetics is difficult. Here, the authors establish a self-sufficient growth selection method and demonstrate its application in engineering the Lactobacillus pentosus NADH oxidase to efficiently recycle reduced nicotinamide mononucleotide (NMNH).

Lignin can be depolymerized into 4-alkylphenols by chemical means. Here the authors show a three-step computational-assisted enzyme engineering process to generate a biocatalyst for the conversion of lignin-derived 4-n-propylguaiacol into isoeugenol, a valuable compound.

In this work the authors provide a computational workflow for the parallel, from scratch, design of proteins to rapidly explore the shape diversity of protein folds.

Reductive stress, reflected by the elevated intracellular NADH/NAD⁺ ratio, is associated with multiple human diseases. Here, the authors develop a genetic tool to manipulate the ratios of cellular NADH/NAD⁺ and NADPH/NADP⁺, and identify purine biosynthesis as an NADH-sensing pathway to mediate reductive stress.

RNA viruses have been responsible for large-scale epidemics and pandemics throughout the last few centuries. Here, the authors show the design, synthesis and screening of artificial RNA endonuclease XNAzymes capable of cleaving genomic SARS-CoV-2 RNA and self-assembling into enzymatic nanostructures inhibiting cellular viral replication.

A challenge in synthetic biology is the empirical characterisation of genetic parts. Here the authors present FPCountR, a validated method and accompanying R package that enables the precise quantification of fluorescent protein reporters per bacterial cell to be enumerated in ‘proteins per cell’ or nanomolar units without requiring protein purification.

Chimeric antigen receptors (CAR) are a promising option for cell-based immunotherapy for cancer and other immune diseases. Here the authors develop speedingCARs, an integrated CAR design and screening platform based on modular signaling domain shuffling and single cell transcriptomic analyses, and test its potential for identifying and validating novel CAR designs.

The induction of long-term systemic immunosurveillance can protect against post-surgery tumor recurrence. Here the authors describe the design of optogenetic-controlled cytokine secreting (IFN-β, TNF-α, and IL-12) engineered mesenchymal stem cells loaded into a hydrogel scaffold, eliciting long-term immune memory and preventing post-operative recurrence in preclinical cancer models.

PCR is an essential method for the amplification and manipulation of nucleic acids, but the requirement for a thermocycler limits access. Here, authors engineer a helicase to replace the heating step of PCR with enzymatic unwinding, allowing the isothermal amplification of fragments up to 6 kb.

Long-duration human space travel creates challenges for maintaining healthy diets. Here the authors discuss using synthetic biology approaches to modify yeast into an optimal, and enjoyable, food production platform.

G protein-coupled receptors (GPCRs) enable cells to sense environmental cues and are indispensable for coordinating vital processes including quorum sensing, proliferation, and sexual reproduction. Here the authors, using heterologous GPCR expression and endogenous ligand production, enable synthetic mating in haploid yeast, and GPCR-mediated biosensing in diploid probiotic yeast.

The immunoglobulin domain framework of antibodies has been a long standing design challenge. Here, the authors describe design rules for tailoring these domains and show they can be accurately designed, de novo, with high stability and the ability to scaffold functional loops.

Applications of the SCRaMbLE process are hindered due to the lack of facile and tight regulation and limited understanding of key factors that may affect the rearrangement outcomes. Here the authors present an approach to precisely regulate SCRaMbLE recombination in a dose-dependent manner using genetic code expansion technology with low basal activity.

“Intracellular phase separation is emerging as a universal principle for organizing biochemical reactions in time and space. Here the authors show that PopZ condensate dynamics support cell division and using PopZ modular architecture, the tunable PopTag platform was developed to enable designer condensates.”

Computational properties of neuronal networks have been applied to computing systems using simplified models comprising repeated connected nodes. Here the authors create layered assemblies of genetically encoded devices that perform non-binary logic computation and signal processing using combinatorial promoters and feedback regulation.

Stably silenced genes with methylated CpG at the promoter are refractory to current CRISPR activation systems. Here the authors create a more robust activation system, TETact that recruits DNA-demethylating TET1 with transcriptional activators.

DNA data storage is a rapidly developing technology with great potential due to its high density, long-term durability, and low maintenance cost. Here the authors present a strand assembly algorithm (DBGPS) using de Bruijn graph and greedy path search.

Arising through multiple binding elements, multivalency can specify the avidity, duration, cooperativity, and selectivity of biomolecular interactions, but quantitative prediction and design of these properties has remained challenging. Here the authors enable facile analysis and engineering of multivalent binding by developing MVsim, a simulator that incorporates biochemical and biophysical parameters of interacting molecules and is accessible through a graphical user interface.

CRISPR gene activation and inhibition has become a powerful synthetic tool for influencing the expression of native genes for foundational studies, cellular reprograming, and metabolic engineering. Here the authors demonstrate near leak-free, inducible expression of a polycistronic array containing up to 24 gRNAs from two orthogonal CRISPR/Cas systems.

De novo development of a simplified photosynthetic reaction center protein can clarify practical engineering principles needed to build enzymes for efficient energy conversion. Here, the authors develop an artificial photosynthetic reaction center that functions without the need for sacrificial electron donors or acceptors.

Toe-hold-mediated strand displacement (DSD) is a widely used molecular tool in applications such as DNA computing and nucleic acid diagnostics. Here the authors characterize dozens of orthogonal barcode sequences that can be used for monitoring the output kinetics of multiplexed DSD reactions in real-time using a commercially-available portable nanopore array device.

Base editing is promising for gene therapy, but in vivo delivery has been limiting. Here the authors perform structure-based rational engineering of the cytosine base editing system Target-AID to minimise off-target effects and decrease its size.

In vitro library screening is a powerful approach to identify functional biopolymers, but only covers a fraction of possible sequences. Here, the authors use experimental in vitro selection results to train a conditional variational autoencoder machine learning model that generates biopolymers with no apparent sequence similarity to experimentally derived examples, but that nevertheless bind the target molecule with similar potent binding affinity.

Whole-genome recoding has been shown to enable nonstandard amino acids, biocontainment and viral resistance in bacteria. Here the authors extend this to human cells using base editing to convert TAG to TAA for 33 essential genes via a single transfection followed by examining base-editing genome-wide.

Acquired resistance to cetuximab can be mediated by generation of mutations in the EGFR ectodomain. Here the authors report a structure-guided and phage-assisted evolution approach for cetuximab evolution to reverse resistance without altering the binding epitope or undermining antibody efficacy.

The invention of the Fourier integral in the 19th century laid the foundation for modern spectral analysis methods. Here the authors develop frequency-based methods for analyzing the reaction mechanisms within living cells from distinctively noisy single-cell output trajectories and present forward engineering of synthetic oscillators and controllers.

Functional annotation of the vast noncoding landscape of the diploid human genome still remains a major challenge of genomic research. Here the authors present a scarless, biallelic, and 100 kb-scale mutagenesis in human cells that uncovers functional significances of endogenous introns and retrotransposons in the chromatin context.

Site-specific recombination (SSR) is an important tool in synthetic biology, but its applications are limited by the inability to predictably tune SSR reaction rates. Here, using quantitative high-throughput experiments and machine learning, the authors achieve rational control of a DNA attachment site sequence to predictably modulate site-specific recombination rates both in vitro and in cells.

Bioluminescence imaging of neuronal activity is desired. Here the authors report a luciferase prosubstrate activatable in vivo by nonspecific esterase and engineer a bioluminescent indicator with responsiveness to calcium ions: integration of these components enabled imaging of neuronal activity in mice.

The range of available copy numbers for cloning vectors is largely restricted to the handful of ORIs that have been isolated from plasmids found in nature. Here the authors introduce a plasmid system that allow for the continuous, finely-tuned control of plasmid copy number between 1 and 800 copies per cell.