Figure 2.

Assay for MusD gene products and retrotransposition. (A) Structure of the MusD expression vector and neo^TNF-marked reporter. (B) Western blot analysis of the Gag-related gene products from the nine coding-competent MusD copies (see Table 1 for copy and accession nos). Lysates of cells transfected with a control plasmid (pCMVβ; mock) or the expression vectors for the coding-competent MusD copies were electrophoresed in a denaturing polyacrylamide gel (SDS-PAGE), blotted, and hybridized with a rabbit anti-serum directed against the Gag polyprotein. The apparent molecular masses of the major bands are indicated. (C) Assay for retrotransposition of the defective neo^TNF-marked MusD reporter upon transcomplementation by the coding-competent MusD copies. Retrotransposition was assayed in heterologous human cells upon cotransfection of the reporter with a control plasmid (pCMVβ) (data not shown) or expression vectors for the selected MusD elements. Results of the G418 selections are illustrated with images of the plates after the G418^R foci have been fixed and stained. The retrotransposition frequencies, as derived from the number of foci per seeded cells, are given for each construct as the mean of two to four independent experiments, carried out with at least 3 × 10⁶ cells, with standard errors indicated.