Figure 9.

Overexpression of rnh1 relieves replication pausing. A–D, 2DNAGE of four restriction fragments of Drosophila S2 cells mtDNA, probed as indicated, in material from control cells and cells overexpressing RNase H1 in the form of epitope-tagged RNase H1-V5 (denoted OE), both treated with 500 μm CuSO₄ for 48 h to induce expression. E, schematic map of Drosophila mtDNA, as also shown in Fig. 8, indicating the location of relevant restriction sites (open circles), mTTF-binding sites (bs1 and bs2; filled circles), the noncoding region (bold), and the probes used. The open arrowhead marks the location and direction of replication initiation (see Ref. 40). The directions of first- and second-dimension electrophoresis in all gels are as indicated by the arrows. The images show relatively low exposures to reveal fine details of the arcs of RIs.