Molecular Cloning of an Apolipoprotein B Messenger RNA Editing Protein

Abstract

Mammalian apolipoprotein B (apo B) exists in two forms, each the product of a single gene. The shorter form, apo B48, arises by posttranscriptional RNA editing whereby cytidine deamination produces a UAA termination codon. A full-length complementary DNA clone encoding an apo B messenger RNA editing protein (REPR) was isolated from rat small intestine. The 229-residue protein contains consensus phosphorylation sites and leucine zipper domains. HepG2 cell extracts acquire editing activity when mixed with REPR from oocyte extracts. REPR is essential for apo B messenger RNA editing, and the isolation and characterization of REPR may lead to the identification of other eukaryotic RNA editing proteins.

APOBEC3 genes: retroviral restriction factors to cancer drivers

“…The founding member, A1 was cloned over 20 years ago and shown to be responsible for the deamination (see Glossary) of cytidine 6666 in the ApoB mRNA, converting it to uridine and generating a stop codon that creates a shorter ApoB 48 protein [2,3]. AICDA encodes Activationinduced Deaminase (AID) which deaminates deoxycytidine (dC) in single stranded (ss) DNA, generating deoxyuridine (dU), an activity that underlies somatic hypermutation (SHM) and class switch recombination (CSR) to drive antibody diversification in B-lymphocytes (reviewed in [4,5]).…”

Expression of activation-induced cytidine deaminase in human hepatocytes via NF-κB signaling

“…Activation-induced cytidine deaminase (AID) is a member of the cytidine deaminase family (Muramatsu et al, 1999) and is closely related to apolipoprotein B RNA-editing cytidine deaminase 1, which converts cytosine nucleotides to uracils in RNA (Teng et al, 1993). AID is expressed in activated B cells, especially in germinal centers and induces somatic hypermutation (SHM), untemplated point mutations, at a high frequency of 10 À3 -10 À4 per base pair, into the variable regions of immunoglobulin genes (Muramatsu et al, 2000;Revy et al, 2000;Kinoshita and Honjo, 2001;Honjo et al, 2002).…”

Biochemical and molecular characterization of two cytidine deaminases in the nematode Caenorhabditis elegans

“…In mammals, one member of the family (apobec-1) has acquired an additional role in the editing of apolipoprotein B (apoB) mRNA [1]. In this process, a cytidine (C6666) is deaminated to a uridine, resulting in the production of two proteins (apoB100 and apoB48) with differing functions from a single mRNA.…”