The KDM4 subfamily of JmjC domain-containing demethylases mediates demethylation 
of histone H3K36me3/me2 and H3K9me3/me2. Several studies have shown that human 
and yeast KDM4 proteins bind to specific gene promoters and regulate gene 
expression. However, the genome-wide distribution of KDM4 proteins and the 
mechanism of genomic-targeting remain elusive. We have previously identified 
Drosophila KDM4A (dKDM4A) as a histone H3K36me3 demethylase that directly 
interacts with HP1a. Here, we performed H3K36me3 ChIP-chip analysis in wild type 
and dkdm4a mutant embryos to identify genes regulated by dKDM4A demethylase 
activity in vivo. A subset of heterochromatic genes that show increased H3K36me3 
levels in dkdm4a mutant embryos overlap with HP1a target genes. More 
importantly, binding to HP1a is required for dKDM4A-mediated H3K36me3 
demethylation at a subset of heterochromatic genes. Collectively, these results 
show that HP1a functions to target the H3K36 demethylase dKDM4A to 
heterochromatic genes in Drosophila.