HP1a binds independently of H3K9me to promoters and spreads H3K9me-dependently into gene bodies.

<p>(A) HP1a and H3K9me profiles in three illustrative regions of the 4^th chromosome in wild type and <i>Setdb1</i> mutant backgrounds. Numbers along the x-axis denote chromosomal positions along the chromosomes in Mb. The y-axis shows the ChIP enrichment in log₂ ratios. Genes expressed from left to right and vice versa are shown above and below the horizontal lines, respectively. The HP1a methylation-independent promoter peaks are indicated by yellow boxes (B) Average metagene profiles of HP1a, H3K9me2 and H3K9me3 on the 4^th chromosome, region 2L:31,the pericentromeric regions and the euchromatic regions, based on eight enrichment values for each active gene in the respective regions (x-axis). The y-axis shows the ChIP enrichment in log₂ ratios. The first points (IG) of the curves show average values for the intergenic regions upstream of the designated promoters of the genes. The promoter (P) is defined as the 500 bp region upstream of the TSS. The gene bodies are divided into five bins (E1–E5) and the average enrichment in introns (IN) is indicated by the last point of each curve. The average profiles for wild type (solid black), <i>Su(var)3-9</i> mutants (solid gray) and <i>Setdb1</i> mutants (dashed gray) are shown.