Cbx2 stably associates with mitotic chromosomes via a PRC2- or PRC1-independent mechanism and is needed for recruiting PRC1 complex to mitotic chromosomes.
Bottom Line: Depletion of PRC1 or PRC2 protein has no effect on the immobilization of Cbx2 on mitotic chromosomes.We find that the N-terminus of Cbx2 is needed for its recruitment to mitotic chromosomes, whereas the C-terminus is required for its immobilization.Thus these results provide fundamental insights into the molecular mechanisms of epigenetic inheritance.
Affiliation: Department of Chemistry, University of Colorado Denver, Denver, CO 80217-3364.Show MeSH
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Mentions: The Cbx-containing PRC1 complexes are recruited to interphasic chromatin via Cbx-family protein interactions with H3K27me3 mediated by PRC2 (Cao et al., 2002; Wang et al., 2004b; Bernstein et al., 2006; Tavares et al., 2012; Morey et al., 2013). Therefore we asked whether PRC2 is required for the accumulation of Cbx2 protein at mitotic chromosomes. To test the hypothesis, we stably and inducibly expressed both YFP-Cbx2 and Cerulean-H2A fusion proteins in Eed knockout (KO) ES cell lines, which lack the H3K27me3 modification. Z-scan of confocal images showed that YFP-Cbx2 fusion protein was granularly distributed at mitotic chromosomes, consistent with its distribution in wild-type ES cells. Quantitative analysis of Z-stack images showed that (97 ± 5)% of Cbx2 protein was enriched at mitotic chromosomes in Eed KO ES cell lines (Figure 2, B and D), consistent with YFP-Cbx2 associating with mitotic chromosomes in wild-type ES cells (Figure 2, A and D), indicating that a core component of the PRC2 complex, Eed, is not required for accumulation of Cbx2 protein at mitotic chromosomes.
Affiliation: Department of Chemistry, University of Colorado Denver, Denver, CO 80217-3364.