CRISPR (2)

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Graphic showing the workflow of using a pooled AAV CRISPR library in vitro. Step A shows the AAV containing the library with either the gRNA only or gRNA plus Cas9 and infecting cells expressing Cas9 or wild-type. The different guides are represented by different colors in individual cells. Step B shows the results of the positive or negative selection, with only one type of guide (color) being chosen. Step C shows verification using next generation sequencing.
A cartoon of a prime editor with two different edit sequences. The DNA sequences are shown with one strand edited and a 5′ DNA flap, before heteroduplex resolution and DNA repair.  The first edit has an unchanged PAM. This DNA is shown connected to the prime editor by a two-way arrow, indicating that the editor can re-bind. Re-nicking is represented by scissors and would remove the newly edited DNA.  The second edit has an altered PAM. A one-way arrow leads from the prime editor to this edit, indicating that the changed PAM prevents the editor from re-binding.
A cartoon overlayed on several crystal structures showing the parts of the prime editor: the Cas9 nickase domain, the reverse transcriptase domain, and the pegRNA.
Alt text: A schematic illustration of the CRISPR/Cas9-based approaches mentioned above. The first illustration (A) shows a DSB made at a transcription start site upstream of an exon. The second illustration (B) shows a DSB made at splice sites. The third illustration (C) shows a DSB made upstream and downstream of an exon to fully remove a genomic fragment. The fourth illustration (D) shows a DSB made within an exon to insert a synthetic polyadenylation signal. 
CRISPR prime editing schematic.
Schematic of Fragmid assembly process from day one to day four and resulting vector architecture.  On day one fragment plasmids plus a destination vector are assembled using Golden Gate (BbsI). On day two the assembled vector containing a Guide (2xBsmBI), Promoter, N-terminus, Cas protein, C’terminus, and 2A-Selection undergoes an exonuclease V cleanup followed by transformation and plating. On day three two colonies per construct are picked, miniprepped and restriction digested for gel validation/whole plasmid sequencing. Below the assembled vector are examples of six vector architectures including pRDA_512 lentivirus, pRDA_722 lentivirus, pRDA_789 CROPseq lentivirus, pRDA_889 AAV, pRDA_575 Piggyback, and pRDA_791 empty plasmid.
Overview of the parts of CRISPR. The bacterial chromosome encodes a tracrRNA (in some systems including Cas9), Cas proteins, and a CRISPR array. The CRISPR array is composed of identical repeat sequences and variable spacer sequences. The array is transcribed and processed into crRNAs, each including one repeat and one spacer. In bacteria, these crRNAs are bound by Cas proteins (Cas9 shown here). The repeat sequence base pairs with the tracrRNA, and the spacer sequence is used to target complementary DNA sequences. In laboratory settings, an sgRNA includes the crRNA and tracrRNA sequences in a “single-guide RNA” that performs both functions. Cas9 cuts both the target and nontarget DNA strands upstream of the PAM site found in the nontarget strand.
screenshot of various PRIDICT webpages

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