A DnaJ protein, apobec-1-binding protein-2, modulates apolipoprotein B mRNA editing.
Mammalian homologues of DnaJ proteins, also known as Hsp40 proteins, are co-chaperonins that complement Hsp70 chaperone function. Using the yeast two-hybrid system, we cloned an apolipoprotein (apo) B mRNA editing complementation protein, called apobec-1-binding protein-2 (ABBP-2), and found that it is a Class II DnaJ homologue. ABBP-2 binds to apobec-1, ... the mammalian apoB mRNA editase, via its J domain and neighboring G/F domain. It is a ubiquitously expressed protein, and, by transfection analysis of GFP-ABBP-2, we found that the protein is located in both the nucleus and cytosol of transfected cells, with predominance in the nucleus. Down-regulation of ABBP-2 expression in cultured cells inhibits endogenous apobec-1-mediated apoB mRNA editing. Like other Hsp40 proteins, ABBP-2 binds to Hsp70 and has ATPase-stimulating activity. Apobec-1-mediated apoB mRNA editing activity of in vitro tissue extracts requires the presence of Hsp70/ABBP-2. Although exogenously added ATP is not required for editing activity, removal of the endogenous ATP present in these extracts, which disrupts ABBP-2-Hsp70 interaction, completely inhibits editing. ABBP-2 differs from previously described auxiliary proteins (ABBP-1, ACF, and GRY-RBP) in that it does not contain any RNA recognition motifs. Not only is ABBP-2 required for efficient apoB mRNA editing, this newly discovered apobec-1-binding protein may help determine the subcellular distribution and trafficking of apobec-1 via its interaction with the chaperonin Hsp70.
Mesh Terms:
Adenosine Triphosphate, Amino Acid Sequence, Apolipoproteins B, Cloning, Molecular, Down-Regulation, Green Fluorescent Proteins, HSP40 Heat-Shock Proteins, Heat-Shock Proteins, Hydrolysis, Luminescent Proteins, Molecular Chaperones, Molecular Sequence Data, RNA Editing, RNA, Messenger, RNA-Binding Proteins, Recombinant Fusion Proteins, Sequence Homology, Amino Acid, Subcellular Fractions
Adenosine Triphosphate, Amino Acid Sequence, Apolipoproteins B, Cloning, Molecular, Down-Regulation, Green Fluorescent Proteins, HSP40 Heat-Shock Proteins, Heat-Shock Proteins, Hydrolysis, Luminescent Proteins, Molecular Chaperones, Molecular Sequence Data, RNA Editing, RNA, Messenger, RNA-Binding Proteins, Recombinant Fusion Proteins, Sequence Homology, Amino Acid, Subcellular Fractions
J. Biol. Chem.
Date: Dec. 07, 2001
PubMed ID: 11584023
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