Tissue-specific differences in the role of RNA 3 ' of the apolipoprotein BmRNA mooring sequence in editosome assembly

Site-specific editing of apolipoprotein B (apoB) mRNA by the cytidine deami nase, APOBEC-1 is proposed to require interactions of auxiliary protein(s) with an eleven nucleotide element, the mooring sequence, located 3' of the C --> U editing site. An analysis of the RNA sequence dependence for protei n-RNA interactions and editosome assembly in rat liver and the small intest ine demonstrated that the mooring sequence was a minimal requirement for th ese interactions. Sequences 3' of the mooring sequence either interacted wi th 66 kDa and 44 kDa proteins or enhanced the interactions of these protein s with the mooring sequence. The data also suggested tissue-specific differ ences in the relative importance of the 3' cis-acting 'enhancer' elements i n the efficiency or stability of editosome assembly. We propose that the pr eviously demonstrated differences in apoB mRNA editing efficiency and its r egulation in liver and intestine may in part be due to differences in auxil iary protein interactions with apoB mRNA 3' of the mooring sequence. (C) 19 99 Academic Press.