FIG. 1.

Effect of shPML2 expression on PML protein levels and SUMO modification of Sp100 in retrovirally transduced HF cells. Whole-cell extracts from 5 × 10⁴ untreated cells were analyzed by Western blotting for PML, Sp100, hDaxx, and actin. The left panels show PML protein levels in siC, siPML2, and siV cells compared to actin. The major PML isoform is shown by an arrow, with the presumed SUMO-modified species migrating more slowly. The faster-migrating bands detected by 5E10 are definitively identified as lower-molecular-weight PML isoforms by this approach. The lower right panel shows that the levels of hDaxx are unaffected by ablation of PML. The upper right panel illustrates that there are several differences in the pattern of Sp100 isoforms in PML-depleted cells, as discussed in detail in the text. Numbers between the panels show molecular masses in kilodaltons.