Biology subjects

Jacobson, J. M.

Publications and source records attributed to Jacobson, J. M..

9 recordsLinked to original sources

bioRxiv2021

Sub-Picomolar Detection of SARS-CoV-2 RBD via Computationally-Optimized Peptide Beacons

The novel coronavirus SARS-CoV-2 continues to pose a significant global health threat. Along with vaccines and targeted therapeutics, there is a critical need for rapid diagnostic solutions. In this work, we employ deep learning-based protein design to engineer molecular beacons that function as conformational switches for high sensitivity detection of the SARS-CoV-2 spike protein receptor binding domain (S-RBD). The beacons contain two peptides, together forming a heterodimer, and a binding ligand between them to detect the presence of S-RBD. In the absence of S-RBD (OFF), the peptide beacons adopt a closed conformation that opens when bound to the S-RBD and produces a fluorescence signal (ON), utilizing a fluorophore-quencher pair at the two ends of the heterodimer stems. Two candidate beacons, C17LC21 and C21LC21, can detect the S-RBD with limits of detection (LoD) in the sub-picomolar range. We envision that these beacons can be easily integrated with on-chip optical sensors to construct a point-of-care diagnostic platform for SARS-CoV-2.

bioengineering↗

bioRxiv2021

Distillation of MSA Embeddings to Folded Protein Structures with Graph Transformers

AO_SCPLOWBSTRACTC_SCPLOWDetermining the structure of proteins has been a long-standing goal in biology. Language models have been recently deployed to capture the evolutionary semantics of protein sequences. Enriched with multiple sequence alignments (MSA), these models can encode protein tertiary structure. In this work, we introduce an attention-based graph architecture that exploits MSA Transformer embeddings to directly produce three-dimensional folded structures from protein sequences. We envision that this pipeline will provide a basis for efficient, end-to-end protein structure prediction.

synthetic biology↗

bioRxiv2020

Non-Invasive Plasma Glycomic and Metabolic Biomarkers of Post-treatment Control of HIV

Non-invasive biomarkers that predict HIV remission after antiretroviral therapy (ART) interruption are urgently needed. Such biomarkers can improve the safety of analytic treatment interruption (ATI) and provide mechanistic insights into the pathways involved in post-ART HIV control. We identified plasma glycomic and metabolic signatures of time-to-viral-rebound and probability-of-viral-rebound using samples from two independent cohorts. These samples include a large number of post-treatment controllers, a rare population demonstrating sustained virologic suppression after ART-cessation. The signatures remained significant after adjusting for key demographic and clinical confounders. We also confirmed a mechanistic link between biomarkers and HIV latency reactivation and myeloid inflammation in vitro. Finally, machine learning algorithms selected sets of biomarkers that predict time-to-viral-rebound with 74-76% capacity and probability-of-viral-rebound with 97.5% capacity. In summary, we fill a major gap in HIV cure research by identifying non-invasive biomarkers, with potential functional significance, that predict duration and probability of viral remission after treatment interruption.

microbiology↗

bioRxiv2020

Targeted Intracellular Degradation of SARS-CoV-2 RBD via Computationally-Optimized Peptide Fusions

The COVID-19 pandemic, caused by the novel coronavirus SARS-CoV-2, has elicited a global health crisis of catastrophic proportions. With no approved cure or vaccine currently available, there is a critical need for effective antiviral strategies. In this study, we report a novel antiviral platform, through computational design of ACE2-derived peptides which both target the viral spike protein receptor binding domain (RBD) and recruit E3 ubiquitin ligases for subsequent intracellular degradation of SARS-CoV-2 in the proteasome. Our engineered peptide fusions demonstrate robust RBD degradation capabilities in human cells, thus prompting their further experimental characterization and therapeutic development.

bioengineering↗

bioRxiv2019

Robust Genome Editing of Single-Base PAM Targets with Engineered ScCas9 Variants

Programmable CRISPR enzymes are powerful and versatile tools for genome editing. They, however, require a specific protospacer adjacent motif (PAM) flanking the target site, which constrains the accessible sequence space for position-specific genome editing applications, such as base editing and homology-directed repair. For example, the standard Cas9 from Streptococcus pyogenes requires a PAM sequence of 5-NGG-3 downstream of its RNA-programmed target. Recently, three separate Cas9 enzymes (xCas9-3.7, SpCas9-NG, and ScCas9) have been independently engineered or discovered to reduce the PAM specificity to a single guanine (G) nucleotide, thus greatly expanding the number of targetable sequences. In this study, we have employed motifs from closely-related orthologs to engineer and optimize ScCas9 to exhibit enhanced genome editing and higher fidelity. Our engineered variants demonstrate superior activity within gene repression and nucleolytic contexts and possess effective base editing capabilities.

bioengineering↗

bioRxiv2018

A Cas9 with Complete PAM Recognition for Adenine Dinucleotides

CRISPR-associated (Cas) DNA-endonucleases are remarkably effective tools for genome engineering, but have limited target ranges due to their protospacer adjacent motif (PAM) requirements. We demonstrate a critical expansion of the targetable sequence space for a Type-IIA CRISPR-associated enzyme through identification of the natural 5-NAA-3 PAM specificity of a Streptococcus macacae Cas9 (Smac Cas9). We further recombine protein domains between Smac Cas9 and its well-established ortholog from Streptococcus pyogenes (Spy Cas9), as well as an \"increased\" nucleolytic variant (iSpy Cas9), to achieve consistent mediation of gene modification and base editing. In a comparison to previously reported Cas9 and Cas12a enzymes, we show that our hybrids recognize all adenine dinucleotide PAM sequences and possess robust editing efficiency in human cells.

bioengineering↗

bioRxiv2018

ssRNA/DNA-Sensors via Embedded Strand-Displacement Programs in CRISPR/Cas9 Guides

RNA and DNA profiles can help classify a variety of biological states, including disease, metabolism and cell type. In a proof-of-concept study on novel genetically encodable components for detecting single-stranded oligonucleotides, we engineered switchable CRISPR guide RNA (swigRNA) with Cas9 affinity that is conditional on sensing an oligo trigger molecule (trigRNA or trigDNA). RNA- and DNA-sensing swigRNAs that serve as off-to-on and on-to-off switches for Cas9 cleavage were achieved by computational design of hybridization dependencies in the guide. This study highlights functional swigRNA structures that implement toehold-gated strand-displacement with their triggers, and should merit further engineering and kinetic characterization.

bioengineering↗

bioRxiv2018

Divergent PAM Specificity of a Highly-Similar SpCas9 Ortholog

RNA-guided DNA endonucleases of the CRISPR-Cas system are widely used for genome engineering and thus have numerous applications in a wide variety of fields. The range of sequences that CRISPR endonucleases can recognize, however, is constrained by the need for a specific protospacer adjacent motif (PAM) flanking the target site. In this study, we demonstrate the natural PAM plasticity of a highly-similar, yet previously uncharacterized, Cas9 from Streptococcus canis (ScCas9) through rational manipulation of distinguishing motif insertions. To this end, we report a divergent affinity to 5-NNGT-3 PAM sequences and demonstrate the editing capabilities of the ortholog in both bacterial and human cells. Finally, we build an automated bioinformatics pipeline, the Search for PAMs by ALignment Of Targets (SPAMALOT), which further explores the microbial PAM diversity of otherwise-overlooked Streptococcus Cas9 orthologs. Our results establish that ScCas9 can be utilized both as an alternative genome editing tool and as a functional platform to discover novel Streptococcus PAM specificities.

microbiology↗

bioRxiv2017

Chimeric CRISPR guides enhance Cas9 target specificity

Oligonucleotide-guided nucleases (OGNs) have enabled rapid advances in precision genome engineering. Though much effort has gone into characterizing and mitigating mismatch tolerance for the most widely adopted OGN, Streptococcus pyogenes Cas9 (SpCas9), potential off-target interactions may still limit applications where on-target specificity is critical. Here we present a new axis to control mismatch sensitivity along the recognition-conferring spacer sequence of SpCas9s guide RNA (gRNA). We introduce mismatch-evading loweredthermostability guides (melt-guides) and exhibit how nucleotide-type substitutions in the spacer can reduce cleavage of sequences mismatched by as few as a single base pair. Cotransfecting melt-guides into human cell culture with an exonuclease involved in DNA repair, we observe indel formation on a standard genomic target at approximately 70% the rate of canonical gRNA and undetectable on off-target data.

biochemistry↗