H3K9 promotes under-replication of pericentromeric heterochromatin in Drosophila salivary gland polytene chromosomes

We replaced the endogenous histones of Drosophila melanogaster with either histones containing an H3K9R mutation or histones containing an H4K16R mutation to interrogate direct functions for histone residues in salivary gland endoreplication. We performed genomic DNA sequencing in HWT (Histone Wild Type) control, H3K9R, and H4K16R females. We found that H3K9 promotes under-replication of pericentromeric heterochromatin but not along chromosome arms and H4K16 is dispensable for under-replication. Overall design: Experiments were performed on endogenous histone mutants rescued with a wild type (HWT), H4K16R mutant, or H3K9R mutant transgenic arrays. Genomic DNA sequencing experiments were carried out in duplicate.