Transcriptional Adaptor ADA3 of Drosophila melanogaster Is Required for Histone Modification, Position Effect Variegation, and Transcription

ABSTRACT The Drosophila melanogaster gene diskette (also known as dik or dAda3) encodes a protein 29% identical to human ADA3, a subunit of GCN5-containing histone acetyltransferase (HAT) complexes. The fly dADA3 is a major contributor to oogenesis, and it is also required for somatic cell viability. dADA3 localizes to chromosomes, and it is significantly reduced in dGcn5 and dAda2a, but not in dAda2b, mutant backgrounds. In dAda3 mutants, acetylation at histone H3 K9 and K14, but not K18, and at histone H4 K12, but not K5, K8, and K16, is significantly reduced. Also, phosphorylation at H3 S10 is reduced in dAda3 and dGcn5 mutants. Variegation for white (w m4 ) and scute (Hw v ) genes, caused by rearrangements of X chromosome heterochromatin, is modified in a dAda3 + gene-dosage-dependent manner. The effect is not observed with rearrangements involving Y heterochromatin (bw D ), euchromatin (Scutoid), or transvection effects on chromosomal pairing (white and zeste interaction). Activity of scute gene enhancers, targets for Iroquoi transcription factors, is abolished in dAda3 mutants. Also, Iroquoi-associated phenotypes are sensitive to dAda3 + gene dosage. We conclude that dADA3 plays a role in HAT complexes which acetylate H3 and H4 at specific residues. In turn, this acetylation results in chromatin structure effects of certain rearrangements and transcription of specific genes.

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Mutational Analysis of a Histone Deacetylase in Drosophila melanogaster: Missense Mutations Suppress Gene Silencing Associated With Position Effect Variegation

Genetics ◽

10.1093/genetics/154.2.657 ◽

2000 ◽

Vol 154 (2) ◽

pp. 657-668 ◽

Cited By ~ 2

Author(s):

Randy Mottus ◽

Richard E Sobel ◽

Thomas A Grigliatti

Keyword(s):

Drosophila Melanogaster ◽

Histone Deacetylase ◽

Transcriptional Activity ◽

Mutational Analysis ◽

Position Effect ◽

Transcriptional Regulator ◽

Position Effect Variegation ◽

Missense Mutations ◽

Effect Variegation ◽

New Mutations

Abstract For many years it has been noted that there is a correlation between acetylation of histones and an increase in transcriptional activity. One prediction, based on this correlation, is that hypomorphic or null mutations in histone deacetylase genes should lead to increased levels of histone acetylation and result in increased levels of transcription. It was therefore surprising when it was reported, in both yeast and fruit flies, that mutations that reduced or eliminated a histone deacetylase resulted in transcriptional silencing of genes subject to telomeric and heterochromatic position effect variegation (PEV). Here we report the first mutational analysis of a histone deacetylase in a multicellular eukaryote by examining six new mutations in HDAC1 of Drosophila melanogaster. We observed a suite of phenotypes accompanying the mutations consistent with the notion that HDAC1 acts as a global transcriptional regulator. However, in contrast to recent findings, here we report that specific missense mutations in the structural gene of HDAC1 suppress the silencing of genes subject to PEV. We propose that the missense mutations reported here are acting as antimorphic mutations that “poison” the deacetylase complex and propose a model that accounts for the various phenotypes associated with lesions in the deacetylase locus.

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Competition Between Different Variegating Rearrangements for Limited Heterochromatic Factors in Drosophila melanogaster

Genetics ◽

10.1093/genetics/145.4.945 ◽

1997 ◽

Vol 145 (4) ◽

pp. 945-959

Author(s):

Vett K Lloyd ◽

Donald A Sinclair ◽

Thomas A Grigliatti

Keyword(s):

Drosophila Melanogaster ◽

Chromosome Rearrangement ◽

Position Effect ◽

Position Effect Variegation ◽

Euchromatic Region ◽

Single Chromosome ◽

Mosaic Expression ◽

Effect Variegation ◽

Protein Components

Position effect variegation (PEV) results from the juxtaposition of a euchromatic gene to heterochromatin. In its new position the gene is inactivated in some cells and not in others. This mosaic expression is consistent with variability in the spread of heterochromatin from cell to cell. As many components of heterochromatin are likely to be produced in limited amounts, the spread of heterochromatin into a normally euchromatic region should be accompanied by a concomitant loss or redistribution of the protein components from other heterochromatic regions. We have shown that this is the case by simultaneously monitoring variegation of a euchromatic and a heterochromatic gene associated with a single chromosome rearrangement. Secondly, if several heterochromatic regions of the genome share limited components of heterochromatin, then some variegating rearrangements should compete for these components. We have examined this hypothesis by testing flies with combinations of two or more different variegating rearrangements. Of the nine combinations of pairs of variegating rearrangements we studied, seven showed nonreciprocal interactions. These results imply that many components of heterochromatin are both shared and present in limited amounts and that they can transfer between chromosomal sites. Consequently, even nonvariegation portions of the genome will be disrupted by re-allocation of heterochromatic proteins associated with PEV. These results have implications for models of PEV.

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