Biology subjects

Potapov, V.

Publications and source records attributed to Potapov, V..

5 recordsLinked to original sources

bioRxiv2025

Massively Parallel Screens Reveal Factors Influencing the Activity of a Diversity-Generating Retroelement Reconstituted in Escherichia coli

Certain phages and microbes use Diversity-Generating Retroelements (DGRs) for targeted adaptation via a process called mutagenic retrohoming. This process relies on an error-prone reverse transcriptase that specifically misincorporates bases opposite adenines in the RNA template. The resulting mutagenized complementary DNA then integrates into a homologous target gene to introduce mutations at adenine residues. Although the functions of core DGR components are well-defined, we still dont know how other cellular factors influence their activity. To address this, we reconstituted the DGR from the Bordetella phage BPP-1 in Escherichia coli. Our systematic analysis uncovered several cellular factors that influence its activity. By sequencing the cDNA, we discovered the reverse transcriptase is particularly mutagenic in the 5-AAC-3 and 5-ACC-3 contexts, which explains their abundance in natural DGR templates. A transposon sequencing screen identified both positive and negative regulators, including the single-stranded DNA exonuclease ExoI, which unexpectedly inhibits DGR activity through a nuclease-independent mechanism. Using a massively parallel reporter assay, we found that DGR preferentially edits targets located near the replication origin and co-directionally oriented with replication. In the preferred orientation, the target sequence is located on the lagging-strand template, where the extended single-stranded DNA gap likely facilitates base pairing with the incoming complementary DNA. Collectively, these findings advance our understanding of how DGRs function within the cellular context and enabled a 1000-fold improvement in editing efficiency, establishing a foundation for future targeted-mutagenesis applications.

microbiology↗

bioRxiv2023

Highly parallelized construction of DNA from low-cost oligonucleotide mixtures using Data-optimized Assembly Design and Golden Gate

Commercially synthesized genes are typically made using variations of homology-based cloning techniques, including polymerase cycling assembly from chemically synthesized microarray-derived oligonucleotides. Here we apply Data-optimized Assembly Design to the synthesis of hundreds of codon-optimized genes in both constitutive and inducible vectors using Golden Gate Assembly. Starting from oligonucleotide pools, we synthesize genes in three simple steps: 1) Amplification of parts belonging to individual assemblies in parallel from a single pool; 2) Golden Gate Assembly of parts for each construct; and 3) Transformation. We construct genes from receiving DNA to sequence confirmed isolates in as little as 4 days. By leveraging the ligation fidelity afforded by T4 DNA ligase, we expect to be able to construct a larger breadth of sequences not currently supported by homology-based methods which require stability of extensive single-stranded DNA overhangs.

synthetic biology↗

bioRxiv2022

Improving the fidelity of uridine analog incorporation during in vitro transcription.

In vitro transcribed synthetic messenger RNAs (mRNAs) represent a novel therapeutic modality and are currently being evaluated for a wide range of clinical indications. To overcome the inherent immunogenicity of the synthetic mRNAs, as well as to increase the therapeutic efficacy of the molecules, RNA sequence optimization is routinely performed and modified uridine analogs--such as pseudouridine ({Psi}) and N1-methyl-pseudouridine (m1{Psi}), are incorporated in the synthetic mRNA. To decipher the fidelity with which these modifications are incorporated during the in vitro transcription (IVT) process, here, we compared, the incorporation fidelity of uridine, {Psi}, or m1{Psi} in multiple RNA sequences with different single-subunit DNA-dependent RNA polymerases (ssRNAPs). By comparing the incorporation of each modified base to that of the unmodified equivalent, we demonstrate that m1{Psi} is incorporated with higher fidelity than {Psi}. Furthermore, the various ssRNAPs exhibit different error rates; however, the spectrum of mutations observed between the RNAPs is similar. We also show that the array of nucleotide misincorporation is not dependent on the template DNA sequence context and that the distribution of these misincorporated nucleotides is not localized to any specific region along the length of the RNA. Based on our findings, we introduce a novel protocol to improve uridine analog incorporation--without affecting total RNA yield--during IVT. Our proof-of-concept experiments and protocol for higher-fidelity incorporation of uridine analogs during IVT provide guidelines when choosing ssRNAPs for the generation of modified uridine--containing mRNAs in vitro.

molecular biology↗

bioRxiv2021

Programmable Cleavage of Double-stranded DNA by Combined Action of Argonaute CbAgo from Clostridium butyricum and Nuclease Deficient RecBC Helicase from E.coli

Prokaryotic Argonautes (pAgos) use small nucleic acids as specificity guides to cleave single-stranded DNA at complementary sequences. DNA targeting function of pAgos creates attractive opportunities for DNA manipulations that require programmable DNA cleavage. Discovery of mesophilic Argonautes active at physiological temperature places pAgos closer to their possible application for genome editing as a simpler alternative to CRISPR/Cas nucleases. Currently, the use of mesophilic pAgos as programmable DNA endonucleases is hampered by their poor action on double-stranded DNA (dsDNA), mainly due to their inability to invade the DNA duplex. The present study demonstrates that efficient in vitro cleavage of double-stranded DNA by mesophilic Argonaute CbAgo from Clostridium butyricum can be activated via the DNA strand unwinding activity of nuclease deficient mutant of RecBC DNA helicase from Escherichia coli (referred to as RecBexo-C). Properties of CbAgo and characteristics of simultaneous cleavage of complementary DNA strands in concurrence with DNA strand unwinding by RecBexo-C were thoroughly explored using 0.3-25 kb DNA substrates. When combined with RecBexo-C helicase, CbAgo was capable of cleaving target sequences located 11-12.5 kb from the ends of linear dsDNA at 37{o}C. Our study demonstrates that CbAgo with RecBexo-C can be programmed to generate dsDNA fragments flanked with custom-designed single-stranded overhangs suitable for ligation with compatible DNA fragments. At present, the combination of CbAgo and RecBexo-C represents the most efficient mesophilic DNA-guided DNA-cleaving programmable endonuclease for use in diagnostic and synthetic biology methods that require sequence-specific nicking/cleavage of dsDNA at any desired location.

molecular biology↗

bioRxiv2020

Rapid 40 kb genome construction from 52 parts

Large DNA constructs (>10 kb), including small genomes and artificial chromosomes, are invaluable tools for genetic engineering and vaccine development. However, the manufacture of these constructs is laborious. To address this problem, we applied new design insights and modified protocols to Golden Gate assembly. While this methodology is routinely used to assemble 5-10 DNA parts in one-step, we found that optimized assembly permitted >50 DNA fragments to be faithfully assembled in a single reaction. We applied these insights to genome construction, carrying out rapid assembly of the 40 kb T7 bacteriophage genome from 52 parts and recovering infectious phage particles after cellular transformation. The new Golden Gate assembly protocols and design principles described here can be applied to rapidly engineer a wide variety of large and complex assembly targets.

synthetic biology↗