FIGURE 2.

Bmi1 is required for H2Aub deposition and accumulates at repeat-DNA sequences in mouse cortical neurons. A, WT and Bmi1^−/− neurons were analyzed by ChIP for proteins enrichment at satellite repeats, intergenic retroelements, and HoxA7 (positive control). Note the accumulation of Bmi1 and Ring1b at all repeat-DNA sequences, including major and minor satellite repeats. Although HP1 accumulation and H2A^ub and H3K9^me3 deposition were reduced in Bmi1^−/− neurons at all tested loci, BRCA1 accumulation was either unaffected (Minor and Major satellites) or increased (Line, Sine, and IAP). Note the near absence of BRCA1 accumulation at HoxA7.1 and HoxA7.3 in both WT and Bmi1^−/− neurons. B, immunofluorescence analysis showing Bmi1 co-localization with H3K9^me3 in WT mouse cortical neurons at P30 (arrowheads). Scale bar, 10 μm. C, immunofluorescence analysis showing loss of Bmi1 signal and reduced H3K9^me3 labeling in cultured e18.5 Bmi1^−/− mouse cortical neurons when compared with Bmi1^+/− neurons. Scale bar, 10 μm.