Evaluation of ACMG-Guideline-Based Variant Classification of Cancer Susceptibility and Non-Cancer-Associated Genes in Families Affected by Breast Cancer.
Two new FA genes, FANCB and FANCL, have recently been identified, and their discovery has allowed a more detailed study into the molecular architecture of the FA pathway.
The FA core complex comprises two central dimers of the FANCB and FA-associated protein of 100 kDa (FAAP100) subunits, flanked by two copies of the RING finger subunit, FANCL.
Eight FA proteins (FANCA, FANCB, FANCC, FANCE, FANCF, FANCG, FANCL and FANCM) and three non-FA proteins (FAAP100, FAAP24 and HES1) form an FA nuclear core complex, which is required for monoubiquitination of the FANCD2-FANCI dimer upon DNA damage.
Eight FA proteins (FANCA, FANCB, FANCC, FANCE, FANCF, FANCG, FANCL and FANCM) and three non-FA proteins (FAAP100, FAAP24 and HES1) form an FA nuclear core complex, which is required for monoubiquitination of the FANCD2-FANCI dimer upon DNA damage.
However, there are macromolecular differences between the FANCL proteins that may account for the apparent distinctions in core complex requirements between the vertebrate and invertebrate FA pathways.
We report here a FANCL founder variant, anticipated to be synonymous, c.1092G>A;p.K364=, but demonstrated to induce aberrant splicing, c.1021_1092del;p.W341_K364del, that accounts for the onset of FA in 13 cases from South Asia, 12 from India and one from Pakistan.
To address this question, we generated cellular knock-out models of FA core complex components and FANCD2 and found that FANCD2-null mutants display higher levels of spontaneous chromosomal damage and hypersensitivity to replication-blocking lesions than Fanconi anemia complementation group L (FANCL)-null mutants, suggesting that FANCD2 provides a basal level of DNA protection countering endogenous lesions in the absence of monoubiquitination.
Fanconi anemia (FA) is a congenital disorder manifested with elevated sensitivity toward DNA interstrand cross-linking agents, and monoubiquitination of FANCD2 by FANCL is a crucial step in FA-mediated DNA repair.
We found that acquired cisplatin-resistant NSCLC-derived A549/DR cells exhibited markedly enhanced FA and HR repair pathway capacities compared to its parental A549 cells and another independent NSCLC-derived cell line, Calu-1, which possesses a moderate innate resistance to cisplatin. siRNA-mediated silencing of the FA-associated genes FANCL and RAD18 and the HR-associated genes BRCA1 and BRCA2 significantly potentiated the sensitivity of A549/DR cells to cisplatin compared to A549 and Calu-1 cells, suggesting that the acquired cisplatin resistance in A549/DR cells may be attributed to enhanced FA and HR pathway capacities responsible for ICL repair.