Sequence elements required for apolipoprotein B mRNA editing enhancement activity from chicken enterocytes

Mammalian intestinal apolipoprotein B (apoB) mRNA edits codon 2153 from CAA in apoB100 mRNA to a stop codon (UAA) in apoB48 mRNA. By contrast, chicken intestinal apoB mRNA contains a CAA codon at the corresponding site, but i s not edited. Chicken enterocyte S100 extracts fail to edit mammalian apoB RNA, but contain factor(s) which enhance the mammalian enterocytes editing activity. By converting the chicken apoa mooring sequences to the conserved mammalian sequences, the study confirmed that this 11-nucleotide stretch w as necessary and sufficient for minimal RNA editing. Using rat and chicken apoB chimeric constructs, the study revealed that mammalian apoB sequences were required for editing enhancement. In concert with the ag-nucleotide co nserved cassette, the 5' rat apoB element (nucleotides 6615-6629) increased editing at C-6666, and was necessary for editing enhancement of chicken en terocyte S100 extracts. Similarly, the 3' rat apoB element (nucleotides 672 6-6752) was required for editing enhancement of chicken enterocyte S100 ext racts, but to a lesser extent in efficiency, compared to the 5' region, In conclusion, this study identified the sequences required for editing enhanc ement activity from chicken enterocyte S100 extracts. (C) 1999 Academic Pre ss.