Antiviral protein APOBEC3G localizes to ribonucleoprotein complexes found in P bodies and stress granules.
Members of the APOBEC (apolipoprotein B mRNA-editing enzyme catalytic polypeptide 1-like) family of cytidine deaminases inhibit host cell genome invasion by exogenous retroviruses and endogenous retrotransposons. Because these enzymes can edit DNA or RNA and potentially mutate cellular targets, their activities are presumably regulated; for instance, APOBEC3G (A3G) recruitment into high-molecular-weight ribonucleoprotein (RNP) complexes has been shown to suppress its enzymatic activity. We used tandem affinity purification together with mass spectrometry (MS) to identify protein components within A3G-containing RNPs. We report that numerous cellular RNA-binding proteins with diverse roles in RNA function, metabolism, and fate determination are present in A3G RNPs but that most interactions with A3G are mediated via binding to shared RNAs. Confocal microscopy demonstrated that substantial quantities of A3G localize to cytoplasmic microdomains that are known as P bodies and stress granules (SGs) and are established sites of RNA storage and metabolism. Indeed, subjecting cells to stress induces the rapid redistribution of A3G and a number of P-body proteins to SGs. Among these proteins are Argonaute 1 (Ago1) and Argonaute 2 (Ago2), factors that are important for RNA silencing and whose interactions with A3G are resistant to RNase treatment. Together, these findings reveal that A3G associates with RNPs that are found throughout the cytosol as well as in discrete microdomains. We also speculate that the interplay between A3G, RNA-silencing pathways, and cellular sites of RNA metabolism may contribute to A3G's role as an inhibitor of retroelement mobility and as a possible regulator of cellular RNA function.
Gallois-Montbrun
Sarah
S
Department of Infectious Diseases, King's College London School of Medicine, 2nd floor, New Guy's House, Guy's Hospital, London Bridge, London SE1 9RT, United Kingdom.
Kramer
Beatrice
B
Swanson
Chad M
CM
Byers
Helen
H
Lynham
Steven
S
Ward
Malcolm
M
Malim
Michael H
MH
D000071480:APOBEC-3G Deaminase; D000998:Antiviral Agents / Q000378:metabolism; D002460:Cell Line; D003564:Cytidine Deaminase; D003594:Cytoplasmic Granules / Q000378:metabolism / Q000821:virology; D015658:HIV Infections / Q000378:metabolism / Q000517:prevention & control / Q000821:virology; D015497:HIV-1 / Q000472:pathogenicity; D006367:HeLa Cells; D006801:Humans; D002479:Inclusion Bodies / Q000378:metabolism / Q000821:virology; D018613:Microscopy, Confocal; D046912:Multiprotein Complexes; D009700:Nucleoside Deaminases / Q000235:genetics / Q000378:metabolism*; D012313:RNA / Q000378:metabolism; D017393:RNA Editing; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D012261:Ribonucleoproteins / Q000378:metabolism*; D014162:Transfection
D000998:Antiviral Agents; D046912:Multiprotein Complexes; D011994:Recombinant Proteins; D012097:Repressor Proteins; D012261:Ribonucleoproteins; D012313:RNA; D009700:Nucleoside Deaminases; D000071480:APOBEC-3G Deaminase; C464924:APOBEC3G protein, human; D003564:Cytidine Deaminase