The non-LTR retrotransposon LINE-1 (L1) comprises approximately 17% of the human 
genome, and the L1-encoded proteins can function in trans to mediate the 
retrotransposition of non-autonomous retrotransposons (i.e., Alu and probably 
SVA elements) and cellular mRNAs to generate processed pseudogenes. Here, we 
have examined the effect of APOBEC3G and APOBEC3F, cytidine deaminases that 
inhibit Vif-deficient HIV-1 replication, on Alu retrotransposition and other 
L1-mediated retrotransposition processes. We demonstrate that APOBEC3G 
selectively inhibits Alu retrotransposition in an ORF1p-independent manner. An 
active cytidine deaminase site is not required for the inhibition of Alu 
retrotransposition and the resultant integration events lack G to A or C to T 
hypermutation. These data demonstrate a differential restriction of L1 and Alu 
retrotransposition by APOBEC3G, and suggest that the Alu ribonucleoprotein 
complex may be targeted by APOBEC3G.