Knock-out of a gene of interest is a useful gene-editing strategy to validate a gene function, to develop a synthetic lethality model or directly mimic a cancer cell in drug screening. Unfortunately, non-dividing cells and hard-to-transfect cells are a major challenge for such genome-editing. However, there is an ideal solution that deserves to be more popular, the use of adenovirus.

This month, a new leap forward in gene editing has been published in Nature under the title ‘Search-and-replace genome editing without double-strand breaks or donor DNA’. DOI: 10.1038/s41586-019-1711-4. Let’s take a look at prime editing to get a clear overview.

Gene knock-out, which is gene editing leading to loss of function, just requires delivering into cells the 2 CRISPR system actors: the CAS9 endonuclease and the specific guide RNA to target the gene of interest. Thus, simple transfection of CleanCap CAS9 mRNA and gRNA followed by cell isolation with the smart aliquotor is a convenient and robust method. Howevery, what can you do if the cells are hard-to-transfect?

Gemma N. Jones et al has recently published in the British Journal of Cancer an article revealing pRAD50 (Ser635) as a pharmacodynamic biomarker of ATM (AZD0156) and ATR inhibitors (AZD6738) to treat cancers. doi:10.1038/s41416-018-0286-4

Key sensors of DNA damage such as ATM and ATR are targets of choice for drug discovery. A useful screening method is based on synthetic lethality. The pre-screening can be done on convenient HeLa cells.