Inhibition of LINE-1 and Alu retrotransposition by exosomes encapsidating APOBEC3G and APOBEC3F.
Human cytidine deaminases, including APOBEC3G (A3G) and A3F, are part of a cellular defense system against retroviruses and retroelements including non-LTR retrotransposons LINE-1 (L1) and Alu. Expression of cellular A3 proteins is sufficient for inhibition of L1 and Alu retrotransposition, but the effect of A3 proteins transferred in exosomes on retroelement mobilization is unknown. Here, we demonstrate for the first time that exosomes secreted by CD4(+)H9 T cells and mature monocyte-derived dendritic cells encapsidate A3G and A3F and inhibit L1 and Alu retrotransposition. A3G is the major contributor to the inhibitory activity of exosomes, however, the contribution of A3F in H9 exosomes cannot be excluded. Additionally, we show that exosomes encapsidate mRNAs coding for A3 proteins. A3G mRNA, and less so A3F, was enriched in exosomes secreted by H9 cells. Exosomal A3G mRNA was functional in vitro. Whether exosomes inhibit retrotransposons in vivo requires further investigation.
Khatua
Atanu K
AK
Center for AIDS Health Disparities Research, Meharry Medical College, 1005 D. B. Todd Blvd., Nashville, TN 37208, USA.
Taylor
Harry E
HE
Hildreth
James E K
JE
Popik
Waldemar
W
D000071480:APOBEC-3G Deaminase; D020087:Alu Elements; D015496:CD4-Positive T-Lymphocytes / Q000378:metabolism; D002460:Cell Line; D003564:Cytidine Deaminase / Q000378:metabolism*; D043525:Cytosine Deaminase / Q000378:metabolism*; D003713:Dendritic Cells / Q000378:metabolism; D055354:Exosomes / Q000201:enzymology* / Q000235:genetics*; D006801:Humans; D020084:Long Interspersed Nucleotide Elements; D010957:Plasmids / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012190:Retroviridae / Q000235:genetics
D012333:RNA, Messenger; C492906:APOBEC3F protein, human; D043525:Cytosine Deaminase; D000071480:APOBEC-3G Deaminase; C464924:APOBEC3G protein, human; D003564:Cytidine Deaminase