RETROVIRUS-LIKE END PROCESSING OF THE TOBACCO TNT1 RETROTRANSPOSON LINEAR INTERMEDIATES OF REPLICATION

The tobacco retrotransposon Tnt1 can transpose through an RNA intermed iate in the heterologous host Arabidopsis thaliana. We report here the identification and characterization of extrachromosomal linear and ci rcular DNA forms of Tnt1 in this heterologous host. Our results demons trate that Tnt1 linear intermediates possess two extra base pairs at e ach end compared with Tnt1's integrated forms. Prior to integration in to the host genome, the two terminal nucleotides at the 3' end of thes e linear intermediates are removed, as in the case of the yeast Ty3 re trotransposon and of retroviruses. Our data, together with those from recent studies of Ty3, reinforce the idea that 3' dinucleotide cleavag e is not restricted to retroviral integrases and is probably a feature shared by many different retrotransposons' enzymes.