TAF10 and TAF10b partially redundant roles during Drosophila melanogaster morphogenesis.

Transcription of eukaryotic genes requires the cooperative action of the RNA polymerase complex, the general transcription factors (TFIIB, TFIID, TFIIE, TFIIF and TFIIH) and chromatin modifiers. The TFIID complex contributes to transcriptional activation by several mechanisms and has a subunit with associated histone acetyltransferase (HAT) activity. The histone modifier SAGA complex has both HAT and deubiquitylase (DUB) activities. TFIID and SAGA share several TBP-associated factors (TAFs), but not their HAT subunit. Recently, several duplicated TAF proteins have been identified in higher eukaryotes, but their functional diversity has been so far poorly characterized. Here, we report the functional similarities and differences of TAF10 and TAF10b, the two TAF10 orthologs of Drosophila melanogaster. Results from in silico modeling suggest that dTAF10 and dTAF10b have similar secondary structures characterized by the presence of a histone-fold domain. Additionally, dTAF10 and dTAF10b share interaction partners and show similar expression patterns in neuronal tissues. Nonetheless, dTAF10 and dTAF10b seem to have partly distinct functions. To investigate their roles, we generated dTaf10-dTaf10b double-mutants and rescued the mutant flies with transgenes, which allowed the translation of either dTAF10 or dTAF10b protein. We found that the loss of dTAF10b resulted in pupal lethality, while animals lacking dTAF10 were able to form puparium. dTaf10 mutant adults showed distorted eye morphology. During DNA repair, dTAF10 and dTAF10b act redundantly, suggesting that these proteins have distinct but partially overlapping functions.

Genes of the ecdysone biosynthesis pathway are regulated by the dATAC histone acetyltransferase complex in Drosophila.

Uncovering mechanisms that regulate ecdysone production is an important step toward understanding the regulation of insect metamorphosis and processes in steroid-related pathologies. We report here the transcriptome analysis of Drosophila melanogaster dAda2a and dAda3 mutants, in which subunits of the ATAC acetyltransferase complex are affected. In agreement with the fact that these mutations lead to lethality at the start of metamorphosis, both the ecdysone levels and the ecdysone receptor binding to polytene chromosomes are reduced in these flies. The cytochrome genes (spookier, phantom, disembodied, and shadow) involved in steroid conversion in the ring gland are downregulated, while the gene shade, which is involved in converting ecdysone into its active form in the periphery, is upregulated in these dATAC subunit mutants. Moreover, driven expression of dAda3 at the site of ecdysone synthesis partially rescues dAda3 mutants. Mutants of dAda2b, a subunit of the dSAGA histone acetyltransferase complex, do not share phenotype characteristics and RNA profile alterations with dAda2a mutants, indicating that the ecdysone biosynthesis genes are regulated by dATAC, but not by dSAGA. Thus, we provide one of the first examples of the coordinated regulation of a functionally linked set of genes by the metazoan-specific ATAC complex.