Cis- and trans-regulation by histone H4 basic patch R17/R19 in metazoan development

Area of Science:

• Epigenetics and Molecular Biology
• Developmental Biology
• Genetics

Background:

• The histone H4 basic patch, composed of positively charged residues, is crucial for chromatin structure and gene regulation.
• The specific biological roles and regulatory mechanisms of H4 residues R17 and R19 remain largely uncharacterized.

Purpose of the Study:

• To investigate the physiological functions of H4 residues R17 and R19 in Drosophila.
• To identify downstream regulatory genes affected by mutations in H4 R17 and R19.
• To elucidate the mechanisms by which these residues regulate gene expression during development.

Main Methods:

• Histone mutagenesis was employed to create mutations at H4 residues R17 and R19 (R17A/E/H, R19A/E/H).
• Phenotypic analysis included assessment of growth defects and chromosomal structures.
• RNA-sequencing (RNA-seq) was used to analyze gene expression changes.
• Western blot and cytological analyses were performed to examine histone modifications and offspring viability.

Main Results:

• Histone mutations at R17 and R19 led to various growth defects and abnormalities in higher-order chromosomal structures.
• The R17E mutation resulted in embryonic lethality.
• RNA-seq revealed overlapping downregulated genes in R17A and R19A mutants, enriched in development-related pathways.
• R17A mutation decreased H4K16 acetylation and male offspring, suggesting a role in male dosage compensation.
• R19 mutation impacted Gpp (Dot1 homologue)-mediated H3K79 methylation, indicating potential histone crosstalk.

Conclusions:

• The positive charges of H4 basic patch residues R17 and R19 differentially regulate gene transcription during Drosophila development.
• R17 is implicated in H4K16 acetylation and male dosage compensation.
• R19 influences H3K79 methylation, potentially via histone crosstalk mechanisms.