Journal: Nucleic Acids Research
Article Title: High-throughput methods enabling random duplications, deletions, or nucleotide-constrained mutagenesis of entire DNA motifs
doi: 10.1093/nar/gkag236
Figure Lengend Snippet: RADDIM creates random duplications or deletions at one random position within a circular DNA molecule. ( A ) Illustration of the RADDIM workflow when starting from a plasmid template. Illustration created with BioRender.com . ( B ) An ExoChase-treated pUC19 plasmid (Fig. ) containing a CcdB toxin gene was nicked on the forward DNA-strand by the site-specific nickase Nt.BbvCI. The resulting double-nicked plasmids were incubated with Bst DNAP, with or without either the 5′–3′ single-strand-specific RecJ exonuclease, or the 3′–5′ single-strand-specific Thermolabile Exonuclease I, to determine if single-strand exonucleases could remove unwanted DNA-amplifications during a convergent nick-translation reaction. ( C ) Characterization of the DNA-ends that were created by a convergent nick-translation reaction using Bst DNAP and either RecJ or Thermolabile Exo I (Fig. ). ConNickTra linearized plasmids were purified and T7 DNAP was used to repair all DNA-ends. Next, T4 DNA ligase was used to re-circularize the linear plasmids, which were transformed into CcdB-sensitive E. coli cells. This selected for plasmids with a mutation in the ccdB toxin gene. The ccdB gene of 40 successfully sequenced plasmids from the RecJ library ( n = 40), and 39 successfully sequenced plasmids from the Thermolabile Exo I library ( n = 39) were sequenced by single-colony Sanger sequencing. ( D ) A synthetic 196 bp dsDNA fragment was incubated together with Bst DNAP alone, and/or Thermolabile Exo I, for 3 h with or without 1 mM MnCl 2 , to evaluate if manganese could reprogram the Bst DNAP and/or ExoI to degrade the ends of linear DNA molecules. ( E ) A pUC19 plasmid containing a CcdB toxin gene was randomly linearized by a ConNickTra reaction using Bst DNAP and ExoI, followed by an addition of 1 mM MnCl 2 for 10–30 min. After a T7 DNAP-mediated DNA end-repair, and a T4 DNA ligase-mediated re-circularization, plasmids were transformed into CcdB-sensitive E. coli cells. ( F ) The ccdB gene of 25 successfully sequenced plasmids from the 10 min library ( n = 25), 21 plasmids from the 20 min library ( n = 21), and 22 successfully sequenced plasmids from the 30 min library ( n = 22) were analyzed by single-colony Sanger sequencing.
Article Snippet: The RADDIM PacBio Revio deep sequencing data analysis and the Python scripts used to calculate the theoretical mutational landscapes possible with NSM are available from the Novo Nordisk Foundation Center for Biosustainability (DTU Biosustain) GitHub for this project ( https://github.com/biosustain/raddim ) and on Zenodo ( https://doi.org/10.5281/zenodo.18863538 ).
Techniques: Plasmid Preparation, Incubation, Nick Translation, Purification, Transformation Assay, Mutagenesis, Sequencing