Fig. 3.

Effect of mutations on the CDA activity and retrotransposition inhibitory activity of A3A and A3B. (A) This assay measures the ability of the indicated wild-type or mutant A3B and A3A proteins to enhance mutagenesis in bacteria (40). Plasmids encoding the indicated proteins were introduced into E. coli, and their expression was activated by using isopropyl β-d-thiogalactoside. The level of mutation induced by each protein was then assessed by plating the bacteria on plates containing rifampicin and counting the number of resistant colonies. (B) Effect of the indicated wild-type or mutant A3A and A3B proteins on retrotransposition of human LINE-1 or the murine LTR retrotransposon IAP. This analysis of IAP retrotransposition frequency was performed as described in ref. 23. The average of three independent experiments is shown.