FBL facilitates interstrand DNA crosslink repair by 2’-O-methylating FANCD2 mRNA

DNA interstrand cross-links (ICLs) are highly cytotoxic DNA lesions implicated in cancer and degenerative diseases. The Fanconi anemia (FA) pathway is the primary repair mechanism for ICLs, with FANCD2 monoubiquitination being crucial for the activation of this pathway. However, the role of epitranscriptional regulation in ICL repairs remains poorly understood. In this study, we demonstrate that the 2’-O-methyltransferase fibrillarin (FBL) is downregulated in FA patients. We further reveal that FBL promotes ICL repair induced by mitomycin (MMC) and cisplatin. Mechanistically, FBL mediates 2’-O-methylation at position 2837 within the protein-coding region of FANCD2 mRNA, thereby enhancing its stability. This modification extends FANCD2 mRNA half-life, resulting in increased FANCD2 protein expression and enhanced formation of FANCD2 foci, which are critical for recruiting Tip60 and BRCA2 to DNA damage sites, ensuring efficient ICL repair. Notably, patients with acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS), which are major complications associated with FA, frequently harbor the R207S mutation in the FBL protein. This mutation significantly impairs its 2’-O-methyltransferase activity. Taken together, our findings uncover a novel epitranscriptional mechanism governing ICL repair, wherein FBL-dependent methylation of FANCD2 mRNA ensures genomic stability. This represents a previously unrecognized role of FBL in ICL repair. These results not only expand our understanding of FA pathway regulation but also provide insights into the molecular basis of FA-related hematologic disorders. A novel epitranscriptional mechanism governing interstrand DNA crosslink repair, wherein FBL-dependent methylation of FANCD2 mRNA ensures genomic stability.