A1CF (APOBEC1 complementation factor) is an essential RNA-binding protein that serves as a key component of the apolipoprotein B mRNA editing complex, where it docks the catalytic subunit APOBEC1 to enable cytosine-to-uracil editing and protects edited mRNA from nonsense-mediated decay 1. Beyond its canonical role in apoB editing, A1CF functions as a broad post-transcriptional regulator with significant pathological implications. A1CF overexpression in hepatocytes promotes steatosis, fibrosis, and hepatocellular carcinoma development through altered polysomal RNA distribution and increased expression of lipogenic, inflammatory, and proliferative genes 1. The protein also coordinates with HNF1A to regulate a transcription-splicing axis critical for pancreatic β-cell function, which is disrupted in type 2 diabetes 2. A1CF variants are associated with gout susceptibility through effects on serum uric acid levels 3. In cancer, A1CF promotes tumor cell proliferation and colony formation through various mechanisms, including DKK1-MEK/ERK signaling in renal cell carcinoma 4 and IL-6 upregulation in breast cancer cells 5. The protein's subcellular localization is regulated by an EIYMNVPV motif, with cytoplasmic variants showing distinct oncogenic properties 5.