Transcription profiling by array of mouse embryonic fibroblasts expressing CBX8 or BMI1

The polycomb group proteins form large repressive complexes. It has recently become evident, via ChIP on chip analysis, that the polycomb complexes, PRC1 and PRC2, target a large number of genes (Boyer et al., 2006; Bracken et al., 2006; Tolhuis et al., 2006), which are involved in cell fate decisions. In order to identify genes which are truly regulated by the polycomb group proteins, CBX8 and BMI1, we expressed these two proteins in mouse embryonic fibroblasts (MEFs) by retroviral infection.