XMRV facilitates the transfer of MLV-based LNCE to naïve cells.

<p>A. The scheme of the experimental approach. DU145LNCE and DU145XMRV were generated by infecting DU145 cells with LNCE and XMRV respectively. The supernatant from DU145XMRV or fresh DU145 cells was applied onto DU145LNCE cultures. The treated cells were cultivated for additional week, and the presence of infection LNCE particles in the supernatant was tested by applying the latter to naïve DU145 cells (designated DU145XL or DU145CL respectively). The cells were selected in the presence of G418. No DU145CL cells survived the selection. B. Structure of LNCE<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0003144#pone.0003144-Kandel1" target="_blank">[6]</a>. LTR-MLV long terminal repeat; psi-MLV packaging signal; neo-neomycin resistance gene; CMV–cytomegalovirus promoter/enhancer region; GFP–the gene for enhanced green fluorescent protein. Positions of hybridization probes (thick lines) and PCR products (dotted lines) are shown below and above the diagram respectively. The predicted sizes of the PCR fragments and the distance between the two KpnI sites are indicated. C. Amplification of LNCE LTR from DU145XL cells. The expected product was obtained from the DNA of the pooled G418-resistant cells (lane 1) and several individually expanded clones (lanes 2–4), but not the original DU145 (lane 5). D. Amplification of an internal LNCE provirus fragment from DU145XL cells. The product was obtained from the DNA of DU145XL (lane 1), but not the naïve DU145 (lane 2). E. Detection of transmission of LNCE in the presence of XMRV by Southern blotting. Hybridization with the probe derived from the GFP fragment was performed on KpnI-digested DNA from DU145 (lane 1), DU145XMRV (lane 2), DU145LNCE (lane 3) and DU145XL (lane 4).