text: In vitro methylation of an IRF-4 promoter-reporter construct decreases its activity
  To provide evidence for a direct effect of methylational status on IRF-4 promoter activity we performed reporter gene assays with IRF-4 promoter constructs before and after their in vitro methylation. A complete methylation of these constructs was checked via restriction assays with methylation-sensitive endonucleases (Figure 5A). Intriguingly, methylation of the IRF-4 promoter significantly decreased promoter activity in IRF-4-positive SD-1 cells by 85.0% (Figure 5B). The silencing effect of CpG methylation was not restricted to IRF-4-positive cells, since in vitro methylation led to a 92.9% abrogation of promoter activity in IRF-4-negative Jurkat cells (Figure 5C). In contrast, control methylation of a reporter construct with a different promoter (FasL) as well as an empty vector had no effect on the reporter activity (data not shown). These data proved a direct association between methylation and activity of the IRF-4 promoter. 
  