Figure 6.

Point mutations in the C-module abolish retrotransposition. (A) Retrotransposition activities of TRE5-A^bsr elements carrying C-module mutations. In this experiment polyclonal G418^R cells expressing the indicated TRE5-A^bsr master elements were cultured in blasticidin-containing medium. Retrotransposition activity was determined by counting the numbers of bsr^R clones per 10⁷ cells, normalized to a copy number of 100 integrated TRE5-A^bsr master elements. The retrotransposition frequencies are presented as means ± SD. (B) Expression of TRE5-A^bsr elements carrying C-module mutations. Total RNA was isolated from pools of G418^R clones transformed with TRE5-A^bsr elements 8, 9, 12 and 13. The synthesis of cDNA was performed using primer bsr5 and PCR on cDNA preparations was carried out using the primers bsr1 and bsr5 as indicated. PCR fragments produced from plasmid-borne mbsr and mbsrI were used as size markers.