Apolipoprotein (apo) B mRNA editing is the deamination of C6666 to uridine, which results in translation of the apoB-48 protein instead of the genomically encoded apoB-100. ApoB-48-containing lipoproteins are cleared more rapidly from plasma and are less atherogenic than apoB-100-containing low-density lipoproteins (LDLs). In humans, the intestine predominantly produces apoB-48 whereas the liver secretes apoB-100 only. To evaluate a potential therapeutic use for liver-induced apoB mRNA editing in humans, we investigated the efficiency and safety of transgenic expression of apoB mRNA-editing enzyme catalytic polypeptide 1 (APOBEC-1) in the absence of endogenous editing in the mouse model. Here we show that regulatable tetO-mediated APOBEC-1 expression in the livers of gene-targeted mice lacking endogenous APOBEC-1 results in 30% apoB mRNA editing. In a time-course experiment, the expression of tetO-APOBEC-1 mRNA was suppressed within 2 days after mice were fed doxycycline and apoB mRNA editing and apoB-48 formation were suppressed within 4 days. However, tetO-APOBEC-1 expression resulted in regulatable aberrant hyperediting of several cytidines downstream of C6666 in apoB mRNA and in novel APOBEC-1 target 1 (NAT1) mRNA. Several of the cytidines in apoB mRNA were hyperedited to a level similar to that of C6666, although editing at C6666 was lower than that in wild-type mice. These results demonstrate that even moderate APOBEC-1 expression can lead to hyperediting, limiting the single-gene approach for gene therapy with APOBEC-1.
- gene therapy
Abbreviations used: ACF, APOBEC-1 complementation factor; apo, apolipoprotein; APOBEC-1, apolipoprotein B mRNA-editing enzyme catalytic polypeptide 1; GAPDH, glyceraldehyde-3-phosphate dehydrogenase; IDL, intermediate-density lipoprotein; LDL, low-density lipoprotein; NAT1, novel APOBEC-1 target 1; tTA, tetracycline-controlled transactivator; VLDL, very-low-density lipoprotein.
- The Biochemical Society, London ©2003