Posttranslational modification of histones regulates transcription but the exact role
that acetylation of specific lysine residues plays in biological processes in vivo
is still not clearly understood. To assess the contribution of different histone modifications
to transcriptional activation in vivo, we determined the acetylation patterns on the
ecdysone induced Eip74EF and Eip75B genes in Drosophila melanogaster larvae by chromatin
immunoprecipitation. We found that acetylation of histone H3 lysine 23 is localized
to promoters and correlates with endogenous ecdysone induced gene activation. In contrast,
acetylation of lysines 8, 12 and 16 of histone H4 and lysine 9 of histone H3 showed
minor differences in their distribution on the regulatory and transcribed regions
tested, and had limited or no correlation with ecdysone induced transcriptional activity.
We found that dCBP, which is encoded by the nejire gene, acetylates H3 lysine 23 in
vivo, and silencing of nejire leads to reduced expression of the Eip74EF and Eip75B
genes. Our results suggest that acetylation of specific lysine residues of histones
contribute specifically to the dynamic regulation of transcription. Furthermore, along
with previous studies identify CBP dependent H3 lysine 23 acetylation as an evolutionarily
conserved chromatin modification involved in steroid induced gene activation.
