Clone the sgRNA sequence targeting CDK12 (5’-GTGGACAAGTTTGACATTAT-3’) into the pSpCas9(BB)−2A-eGFP (PX458) vector (Addgene 48138).
Order single-stranded oligodeoxynucleotides (G731E: 5’-ttatatacttggccataggttccttctccaataatTTCaataatgtcaaacttgtccacacagcgtttcccccagtc-3’; G731R: 5’-ttatatacttggccataggttccttctccaataatGCGaataatgtcaaacttgtccacacagcgtttcccccagtc-3’) from a commercial vendor.
Nucleofect 1 million A549 cells (using 4D-Nucleofector, Lonza, Basel, Switzerland) with PX458-sgCDK12 (1 microgram) and single-stranded oligodeoxynucleotides (5 microliters of 100 micro-molar stock).
Afterwards, treat cells with 5 µM HQ461 for 2 weeks to select for cells with CDK12G731E/R knock-in.
Isolate clones that survive HQ461 treatment and use Sanger sequencing to confirm to G731E/R genomic conversion.