ASH1, a Drosophila Trithorax Group Protein, Is Required for Methylation of Lysine 4 Residues on Histone H3

Covalent modifications of histone tails modulate gene expression via chromatin organization. As examples, methylation of lysine 9 residues of histone H3 (H3) (H3-K9) is believed to repress transcription by compacting chromatin, whereas methylation of lysine 4 residues of H3 (H3-K4) is believed to ac...

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Published inProceedings of the National Academy of Sciences - PNAS Vol. 100; no. 20; pp. 11535 - 11540
Main Authors Byrd, Kristin Nastase, Shearn, Allen
Format Journal Article
LanguageEnglish
Published United States National Academy of Sciences 30.09.2003
National Acad Sciences
Subjects
Acetylation
Alleles
Animals
Biological Sciences
Chromatin
Chromosomes
DNA-Binding Proteins
Drosophila
Drosophila Proteins
Fluorescent Antibody Technique
Fluorescent antibody techniques
Gene expression
Genetics
Histones
Histones - metabolism
Insects
Lysine - metabolism
Methylation
Mutation
Polytene chromosomes
Proteins
Salivary glands
Transcription Factors - physiology
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Summary:Covalent modifications of histone tails modulate gene expression via chromatin organization. As examples, methylation of lysine 9 residues of histone H3 (H3) (H3-K9) is believed to repress transcription by compacting chromatin, whereas methylation of lysine 4 residues of H3 (H3-K4) is believed to activate transcription by relaxing chromatin. The Drosophila trithorax group protein absent, small, or homeotic discs 1 (ASH1) is involved in maintaining active transcription of many genes. Here we report that in extreme ash 1 mutants, no H3-K4 methylation is detectable. Within the limits of our assays, this lack of detectable H3-K4 methylation implies that ASH1 is required for essentially all H3-K4 methylation that occurs in vivo. We report further that the 149-aa SET domain of ASH1 is sufficient for H3-K4 methylation in vitro. These findings support a model in which ASH1 is directly involved in maintaining active transcription by conferring a relaxed chromatin structure.
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To whom correspondence should be addressed. E-mail: bio_cals@jhu.edu.
Communicated by Philip A. Beachy, Johns Hopkins University School of Medicine, Baltimore, MD, June 11, 2003
Abbreviations: ASH1, absent, small, or homeotic discs 1; HMTase, histone methyltransferase; SU(VAR)3–9, suppressor of variegation 3–9; TRX, trithorax; H3, histone H3; H3-K4, lysine 4 residue of H3; H3-K9, lysine 9 residue of H3; H4-K20, lysine 20 residue of histone H4; anti-H3-K4dm, antidimethyl-H3 (lys4).
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.1933593100