Figure 4. Repeat B, but not A, continues to play a role in maintaining Polycomb across Xi.
See also Figures S1 and S4.
(A) H2AK119ub and H3K27me3 IF combined with Xist RNA FISH in WT Xist, ΔRepA, and ΔRepB female MEFs. n > 100 per deletion cell line, with nearly all cells showing the indicated pattern of enrichment for each mark.
(B) Allele-specific H2AK119ub/H3K27me3 ChIP-seq in WT Xist, ΔRepA, and ΔRepB MEFs.
(C) Zoom-in of allele-specific ChIP-seq tracks in (B).
(D) Boxplots quantifying allele-specific ChIP-seq coverage over X-linked genes. Wilcoxon rank-sum test, p values as shown.
(E) Diagram summarizing roles of Repeats A and B in gene silencing and Polycomb recruitment throughout XCI. Repeat A is required for initial gene silencing and an early wave of Polycomb recruitment; Repeat B is required for sustained gene silencing and Polycomb recruitment. Dashed line indicates uncertain or minimal contribution.