| CUGBP 2 modulates C to U editing of apolipoprotein B mRNA by interacting with apobec 1 and ACF , the apobec 1 complementation factor . ^^^ CUGBP 2 and ACF co fractionate in bovine liver S 100 extracts , and addition of recombinant apobec 1 leads to assembly of a holoenzyme . ^^^ Immunodepletion of CUGBP 2 co precipitates ACF , and these proteins co localize the nucleus of transfected cells , suggesting that CUGBP 2 and ACF are bound in vivo . ^^^ However , addition of recombinant CUGBP 2 to a reconstituted system demonstrated a dose dependent inhibition of C to U RNA editing , which was rescued with either apobec 1 or ACF . ^^^ Antisense CUGBP 2 knockout increased endogenous apoB RNA editing , whereas antisense knockout of either apobec 1 or ACF expression eliminated apoB RNA editing , establishing the absolute requirement of these components of the core enzyme . ^^^ |