FIG. 8.

The HERV-K RT enzyme has RNase H activity. A schematic of the RNase H assay is indicated at the top of the figure. Cleavage of the internally labeled 344-nt RNA transcript at the site of the annealed DNA oligonucleotide will produce a 5′-terminal fragment of 176 nt and a 3′-terminal fragment of 139 nt. The positions of these signals are indicated in the lower panel, which shows an analysis of the RNA cleavage products on a denaturing sequencing gel. The mock-treated RNA is shown in lane 14. We tested increasing amounts (0.1, 0.2, and 1.0 μl) of the GST control (lanes 2 to 4), the HIV-1 GST-RT enzyme (lanes 5 to 7), and the HERV-K 7.1 and 10.1 enzymes (lanes 8 to 10 and 11 to 13, respectively). As a positive control, we used the E. coli RNase H enzyme (Boehringer; 1 μl of 1-U/μl stock) (lane 1).