FBXL12 (UniProt_ID: Q9NXK8) is a largely uncharacterized F-box protein and bioinformatic analysis has revealed that its expression levels correlate with those of Cyclin-E and together play an unfavourable role in patient prognosis in breast cancer. This marks FBXL12 as a potential target for cancer therapy. In an MS-based screen, FANCD2 (Fanconi anaemia complementation group D2) was discovered as an interacting partner of FBXL12. FANCD2 is a protein of the Fanconi anaemia complementation group (FANC), a disorder of the bone marrow that leads to anaemia and other developmental defects. FBXL12 poly-ubiquitylates FANCD2, a modification that causes FANCD2 dissociation from the DNA and subsequent degradation. Presumably, FBXL12 inhibition results in FANCD2 accumulation on DNA that hinders the recruitment of DNA repair factors. The current study aims to focus on the implication of FBXL12-FANCD2 in cancer development and progression, particularly in triple-negative breast cancer cell lines. The role of FBXL12 during replication stress was assessed using stable FBXL12-KO cells, doxycycline regulated shRNAFBXL12 and siRNA-FBXL12-mediated depletion of FBXL12 treated with replication stressinducing drugs, including WEE 1 inhibitor AZD1775. Characterization of a putative phosphorylated FANCD2 site was analysed by Dot-blot and immunoblotting. The data suggest that depletion of FBXL12 sensitize cells to AZD1775-induced replication stress, presumably leading to lethal DNA damage and loss of cellular recovery. It can be concluded that FBXL12-FANCD2 interaction can be exploited as a potential target for cancer therapy to treat aggressive cancer types like triple-negative breast cancers that have poor patient outcomes and limited treatment options available.
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