6570 Nucleic Acids Research, 2011, Vol. 39, No. 15 Figure 1. A lacO-LacI array is an effective RFB in eukaryotes. (A) Schematic showing the position of the ade6- direct repeat and lacO array on chromosome 3 as well as the probes used for the 2D gel analysis in C and F. (B) Images showing (+) and (++) levels of NLS-LacI-eCFP in cells containing the lacO array. The arrowhead indicates an example of a lacO-LacI focus. Cells were analysed after 20 h of LacI induction. (C) Two-dimensional gel analysis of replication intermediates in the BamHI lacO-containing fragment from a wild-type strain with the indicated (continued)