Characterization of molecular attributes that influence LINE-1 restriction by all seven human APOBEC3 proteins

Highlights: • All seven human A3 proteins restrict L1 to varying degrees. • Disruption of A3 oligomerization correlates with reduced L1 restriction. • A3A exhibits both deamination-dependent and -independent L1 restriction. • Binding of A3 proteins to L1 proteins ORF0p, ORF1p and ORF2p was assessed. • Binding of A3 proteins to L1 proteins does not predict restriction intensity. LINE-1 (L1) is a non-long terminal repeat (LTR) retrotransposon inserted throughout the human genome. APOBEC3 (A3) proteins are part of a network of host intrinsic defenses capable of restricting retroviruses and the replication of L1 retroelements. These enzymes inactivate retroviruses primarily through deamination of single-stranded viral DNA. In contrast, only A3A deaminates L1 DNA, while the other six A3 proteins restrict L1 to varying degrees through yet poorly defined mechanisms. Here we provide further insight into the molecular attributes of L1 restriction by A3 proteins. We specifically investigated the roles of A3 protein oligomerization, interactions with RNA and their binding to the various L1 proteins. Our results show that compromising the ability of A3 proteins to oligomerize or interact with a nucleic acid substrate diminished L1 restriction to varying degrees. However the efficiency of their binding to L1 proteins did not predict restriction or the potency of the restriction.