Histone octamer function in vivo: mutations in the dimer-tetramer interfaces disrupt both gene activation and...

Area of Science:

• Molecular Biology
• Genetics
• Cell Biology

Background:

• The histone octamer forms the core of nucleosomes, essential for DNA packaging.
• Specific interactions between histone H4 and H2A-H2B dimers involve tyrosine residues.
• Understanding these interactions is crucial for comprehending gene regulation and cell cycle control.

Purpose of the Study:

• To investigate the in vivo roles of specific tyrosine residues in histone H4 interactions with H2A-H2B dimers.
• To determine the essentiality of these interactions for cell survival and gene expression.

Main Methods:

• Site-directed amino acid substitutions were introduced at critical tyrosine residues on histone H4.
• Temperature-sensitive mutants were generated to study the effects of these mutations.
• Transcriptional analysis was performed to assess gene expression changes in mutant cells.

Main Results:

• Elimination of specific H4-dimer interactions proved lethal, indicating their essential nature.
• Mutations at tyrosine residues resulted in temperature-sensitive phenotypes with significant effects on transcription.
• Mutants exhibited both positive (Spt-, Sin-) and negative effects on gene expression, including critical G1 cell cycle genes (CLN1, CLN2, SWI4, SWI6, CLN3).

Conclusions:

• Histone dimer-tetramer interactions are vital for cellular life in vivo.
• These interactions play a critical role in regulating the expression of genes essential for G1 cell cycle progression.