Synthetic Lethal Interactions for Kinase Deficiencies to DNA Damage Chemotherapeutics.

Kinases are signaling enzymes that regulate diverse cellular processes. As such, they are frequently mutated in cancer and therefore represent important targets for drug discovery. However, until recently, systematic approaches to identify vulnerabilities and resistances of kinases to DNA-damaging chemotherapeutics have not been possible, partially due to the lack of appropriate technologies. With the advent of CRISPR-Cas9, a comprehensive study has investigated the cellular survival of more than 300 kinase-deficient isogenic cell lines to a diverse panel of DNA-damaging agents, enriched for chemotherapeutics. Here, we discuss how this approach has allowed for the rational development of combination therapies that are aimed at using synthetic lethal interactions between kinase deficiencies and DNA-damaging agents that are used as chemotherapeutics.

Map of synthetic rescue interactions for the Fanconi anemia DNA repair pathway identifies USP48.

Defects in DNA repair can cause various genetic diseases with severe pathological phenotypes. Fanconi anemia (FA) is a rare disease characterized by bone marrow failure, developmental abnormalities, and increased cancer risk that is caused by defective repair of DNA interstrand crosslinks (ICLs). Here, we identify the deubiquitylating enzyme USP48 as synthetic viable for FA-gene deficiencies by performing genome-wide loss-of-function screens across a panel of human haploid isogenic FA-defective cells (FANCA, FANCC, FANCG, FANCI, FANCD2). Thus, as compared to FA-defective cells alone, FA-deficient cells additionally lacking USP48 are less sensitive to genotoxic stress induced by ICL agents and display enhanced, BRCA1-dependent, clearance of DNA damage. Consequently, USP48 inactivation reduces chromosomal instability of FA-defective cells. Our results highlight a role for USP48 in controlling DNA repair and suggest it as a potential target that could be therapeutically exploited for FA.

Parallel genome-wide screens identify synthetic viable interactions between the BLM helicase complex and Fanconi anemia.

Maintenance of genome integrity via repair of DNA damage is a key biological process required to suppress diseases, including Fanconi anemia (FA). We generated loss-of-function human haploid cells for FA complementation group C (FANCC), a gene encoding a component of the FA core complex, and used genome-wide CRISPR libraries as well as insertional mutagenesis to identify synthetic viable (genetic suppressor) interactions for FA. Here we show that loss of the BLM helicase complex suppresses FANCC phenotypes and we confirm this interaction in cells deficient for FA complementation group I and D2 (FANCI and FANCD2) that function as part of the FA I-D2 complex, indicating that this interaction is not limited to the FA core complex, hence demonstrating that systematic genome-wide screening approaches can be used to reveal genetic viable interactions for DNA repair defects.