Journal: Frontiers in Microbiology
Article Title: Rescue of Recombinant Adenoviruses by CRISPR/Cas-Mediated in vivo Terminal Resolution
doi: 10.3389/fmicb.2022.854690
Figure Lengend Snippet: ITR-near CTR induced also efficient rescue of recombinant adenoviruses based on HAdV-4. (A) Similarly to the HAdV-5-based constructs (upper panel), a recombinant HAdV-4 based bacmid was constructed (lower panel), which was flanked with ACT sequences (red, PAM is underlined) at both ITRs (here, the right ITR is shown, white letters). This sequence can be targeted by the universal sgRNA-Ex, like for the HAdV-5 based constructs (upper panel). Here also another sgRNA (sgRNA-Int4, blue, PAM is underlined) targeting the HAdV-4 ITRs (bold) can induce Cas9-mediated cleavage at the ITRs (blue triangles). (B) The rAd reconstitution efficiencies were determined after co-transfection of A549, SKOV-3, and 293A cells with pBWH-E4-ΔE3 with either pAR-gRNA-Cas9F-Amp expressing sgRNA-Ex (E4-Ex) or with pAR-Int4-Cas9F-Amp (E4-Int4, for 293A cells only). The primary rescue efficiencies were obtained as in . A549-Ex and SKOV-3-Ex were tested twice in technical duplicates, and error bars represent spread of results. E4-Ex and E4-Int4 were done three times in technical duplicates, and error bars represent standard deviation. Significance was calculated using unpaired t -test comparing E4-Ex and E4-Int4. ** p < 0.01.
Article Snippet: The expression cassette coding for the destabilized, human codon-optimized Cas9 fusion protein (DD-Cas9) was constructed on the basis of pDD-Cas9 [Addgene Plasmid #90086, a kind gift from Raffaella Sordella ( )] by inserting a glutamine codon instead of the first methionine codon of the Cas9 coding sequence.
Techniques: Recombinant, Construct, Sequencing, Cotransfection, Expressing, Standard Deviation
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![(A) Shown is the fold increase in the mean fluorescent intensity (MFI) in Flag-tag-specific FACS measurements of different <t>293A-Cas9</t> clones expressing Flag-tagged Cas9 compared to the parental 293A signal. Data shown represent the mean of two independent experiments, with error bars indicating the range of measurements. All presented clones were also checked for CTR competency of rAd rescue by co-transfecting of pBWH-C5-mChe and pAR-gRNA-Ex. Clones that appeared to be permissive for rAd rescue based on two experiments are indicated by orange bars, while the white bars indicate clones, which appeared to be non-permissive in at least one experiment. (B) Comparison of different approaches for supplying necessary components for CRISPR/Cas9-mediated CTR. Co-transfection of helper plasmid(s) (Helper) expressing sgRNA and <t>Cas9</t> <t>protein</t> with the construct carrying the ACT flanked rAd bacmids (rAd, red bar, this approach was applied for most of the experiments described in the manuscript) was compared to combination of all CTR components in one construct coding for the rAd genome and all necessary CRISPR/Cas9-components in the vector backbone (purple bar); the Cas9 is delivered by constitutive expression in the cell line B2 or b5 [see (A) ] used to rescue the rAd, while a bacmid coding for a rAd genome is co-transfected together with a sgRNA-expressing plasmid as in panel (A) (dark and light orange bars); and the same as in previously, but sgRNA is expressed from the same construct that carries the rAd (dark and light gray bars). The primary rescue efficiencies were obtained as in . Significance was calculated using Welch’s ANOVA test.](https://pub-med-central-images-cdn.bioz.com/pub_med_central_ids_ending_with_5557/pmc08975557/pmc08975557__fmicb-13-854690-g004.jpg)
