FIG. 4.
Formation of the IRF-E–IRF-1 complex in NDV-infected L929 cells. A radiolabeled IRF-E probe from the IL-15 promoter region (CTTTCTCTTTCACTTTCT) was incubated with total cellular extracts from NDV-infected (lanes 3 and 4) and noninfected (lanes 1 and 2) L929 cells. The resulting complex was analyzed on a nondenaturing polyacrylamide gel. When an antibody against IRF-1 was included in the reaction, it supershifted an IRF-E–IRF-1 complex only from NDV-infected L929 cells (lane 4; indicated by the upper arrow). Note the presence of a residual complex in lanes 1 to 4 that was not shifted by the addition of the antibody. This complex was likely to be a nonspecific band since it was present in L929 cell extract both before and after NDV infection. The lower arrow in NDV-infected L929 cells indicates a complex that at least contains IRF-1 protein bound to the IRF-E probe.