Analysis of protein complexes assembled on apolipoprotein B mRNA for mooring sequence-dependent RNA editing.

Apolipoprotein B (apoB) mRNA editing involves a cytidine-to-uridine transition at a select site catalyzed by a cytidine deaminase known as APOBEC-1. This enzyme cannot edit RNA alone but acquires site-specific editing capacity in the context of additional protein factors (auxiliary proteins). These proteins are currently hypothesized to assemble with APBEC-1 as a holoenzyme complex or editosome. Auxiliary proteins are the focus of ongoing research as they presumably serve important structural and regulatory roles in the editosome. The abilities of auxiliary proteins to interact with APOBEC-1 and apoB RNA and to promote RNA editing activity are important endpoints used as proof that proteins are functionally involved in apoB RNA editing. This article reviews the discovery of the editosome and provides detailed protocols for its isolation and subfractionation.