Cloning of an Apobec-1-binding protein that also interacts with apolipoprotein B mRNA and evidence for its involvement in RNA editing.
Apolipoprotein (apo)B mRNA editing is mediated by a multiprotein editosome complex. Apobec-1 is the catalytic component of this complex, but other proteins involved in editing have not been identified. We used the yeast two-hybrid system to identify an apobec-1-interacting protein, ABBP-1. ABBP-1 contains 331 amino acid residues and is identical to a previously reported human type A/B hnRNP except for a 47-residue insertion at its C-terminal region. It contains typical RNP motifs at its N-terminal half and glycine-rich motifs in the C-terminal region. Northern blot analysis indicates that ABBP-1 mRNA is distributed in multiple human tissues. By deletion analysis, we mapped the apobec-1-binding region to the glycine-rich domain. ABBP-1 also binds to apoB mRNA transcripts around the editing site and can be UV-cross-linked to them in vitro. Immnodepletion of ABBP-1 from an active apoB mRNA editing tissue extract inhibits its editing activity. Down-regulation of ABBP-1 in an apobec-1-expressing HepG2 cell line by transfection with an antisense ABBP-1 cDNA construct leads to inhibition of endogenous apoB mRNA editing. We conclude that ABBP-1 is an apobec-1-interacting protein that may play an important role in apoB mRNA editing.
Lau
P P
PP
Departments of Cell Biology and Medicine, Baylor College of Medicine, Houston, Texas 77030, USA.
Zhu
H J
HJ
Nakamuta
M
M
Chan
L
L
D000071479:APOBEC-1 Deaminase; D000595:Amino Acid Sequence; D001055:Apolipoproteins B / Q000235:genetics*; D002460:Cell Line; D003001:Cloning, Molecular; D003564:Cytidine Deaminase / Q000378:metabolism*; D015536:Down-Regulation; D034481:Heterogeneous-Nuclear Ribonucleoprotein Group A-B; D006801:Humans; D008969:Molecular Sequence Data; D017393:RNA Editing / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D000098830:AICDA (Activation-Induced Cytidine Deaminase)
D001055:Apolipoproteins B; C103749:HNRNPAB protein, human; D034481:Heterogeneous-Nuclear Ribonucleoprotein Group A-B; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D000098830:AICDA (Activation-Induced Cytidine Deaminase); D000071479:APOBEC-1 Deaminase; C000605089:APOBEC1 protein, human; D003564:Cytidine Deaminase