In Drosophila, the dSAGA complex containing dADA2b is involved in the acetylation of histone H3, lysines 9 and 14. Curiously, dAda2b mutants have greatly reduced lysine 9- and 14-acetylated histone H3 levels, but these animals survive to late development.
To investigate the molecular effects of loss of histone H3, lysine 9 and 14 acetylation, we compared the global messenger ribonucleic acid (mRNA) profiles of wild-type and dAda2b mutant animals at two developmental stages. Global gene expression profiles show that dSAGA-specific loss of H3-lysine 9 and 14 acetylation results in expression changes (up- or down-regulation) of rather small gene subsets and does not cause global transcriptional deregulation. I'm here. Among the genes upregulated in dAda2b mutants are those that play a role in antimicrobial defense mechanisms. Results from chromatin immunoprecipitation experiments show that in dAda2b mutants, lysine-9-acetylated histone H3 levels are reduced in both up- and down-regulated genes of dSAGA. In contrast, the promoter of the dSAGA-independent ribosomal protein gene of the dAda2b mutant maintains high levels of histone H3K9ac. Our data suggest that dSAGA differentially alters Pol II accessibility to specific promoters by acetylating H3 at lysine 9.
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