ChIP analysis shows that K111 proviruses are found in centromeric and pericentromeric regions. Quantitative PCR of K111 DNA (A), and the centromeric 11-mer alphoid repeat of chromosome 21 (alphoid^Chr.21) DNA (B), immunoprecipitated by antibodies to CENPA and CENPB or control IgG. K111 is enriched ∼15-fold in the CENP protein fractions compared with control IgG (A), while the alphoid^Chr.21 is enriched approximately eightfold (B). Quantitative PCR of 5S ribosomal DNA, present in the q arm of chromosome 1, shows no significant enrichment with antibodies to CENPA and CENPB (C). Quantitative PCR of K111, alphoid^Chr.21, and 5S ribosomal DNA in H3K9me3-associated fractions shows that K111 is enriched ∼170-fold. The 11-mer alphoid^Chr.21 repeat is enriched ∼650-fold in the H3K9me3-associated fractions, while 5S ribosomal DNA shows no significant enrichment (D). Graphs show the relative enrichment normalized to control IgG-precipitated fractions. Asterisks indicate statistical significance: (***) P < 0.001, (**) P < 0.01, (*) P < 0.05, (n.s.) not significant.