Particularly, we found that A3BCF together with ADARB1 cooperate to induce C-to-U editing at MFN1 transcripts, thereby interfering with MFN1 splicing and mediating MFN1 S329L conversion, with robust S329L recoding primarily occurring in naïve B lymphocytes and a subset of primary CLL cells. Here, MFN1 is linked to B-cell chronic lymphocytic leukemia.