Mutagenesis of apobec-1 complementation factor reveals distinct domains that modulate RNA binding, protein-protein interaction with apobec-1, and complementation of C to U RNA-editing activity.
C to U editing of apolipoprotein B (apoB) RNA requires a multicomponent holoenzyme complex in which minimal constituents include apobec-1 and apobec-1 complementation factor (ACF). We have examined the predicted functional domains in ACF in binding apoB RNA, interaction with apobec-1, and complementation of RNA editing. We demonstrate that apoB RNA binding and apobec-1-interacting domains are defined by two partially overlapping regions containing the NH(2)-terminal RNA recognition motifs of ACF. Both apoB RNA binding and apobec-1 interaction are required for editing complementation activity. ACF is a nuclear protein that upon cotransfection with apobec-1 results in nuclear colocalization and redistribution of apobec-1 from the cytoplasm. ACF constructs with deletions or mutations in the putative nuclear localization signal (NLS) still localize in the nucleus of transfected cells but do not colocalize with apobec-1, the latter remaining predominantly cytoplasmic. These observations suggest that the putative NLS motif in ACF is not responsible for its nucleo-cytoplasmic trafficking. By contrast, protein-protein interaction is important for the nuclear import of apobec-1. Taken together, these data suggest that functional complementation of C to U RNA editing by apobec-1 involves the NH(2)-terminal 380 residues of ACF.
Blanc
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Department of Internal Medicine, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
Henderson
J O
JO
Kennedy
S
S
Davidson
N O
NO
D000071479:APOBEC-1 Deaminase; D000818:Animals; D001055:Apolipoproteins B / Q000378:metabolism; D001483:Base Sequence; D002460:Cell Line; D003001:Cloning, Molecular; D003564:Cytidine Deaminase; D017931:DNA Primers; D016296:Mutagenesis; D012313:RNA / Q000378:metabolism*; D017393:RNA Editing; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology*; D051381:Rats; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D017384:Sequence Deletion
D001055:Apolipoproteins B; D017931:DNA Primers; D016601:RNA-Binding Proteins; D011994:Recombinant Proteins; D012313:RNA; D000071479:APOBEC-1 Deaminase; C000605091:Apobec1 protein, rat; D003564:Cytidine Deaminase