Histone supply regulates S phase timing and cell cycle progression.

Area of Science:

• Molecular Biology
• Cell Biology
• Genetics

Background:

• Eukaryotes package DNA into nucleosomes, comprising histone proteins.
• Nucleosomes are disrupted and reassembled during DNA replication.
• Control of chromatin assembly and its coordination with the cell cycle remain unclear.

Purpose of the Study:

• To investigate the role of histone supply in cell cycle regulation.
• To elucidate the mechanism linking histone availability to cell cycle progression.

Main Methods:

• Utilized a histone null mutation in Drosophila melanogaster.
• Employed transgenic histone genes to control histone supply levels.

Main Results:

• Histone supply levels directly regulate the duration of S phase.
• Lack of de novo histone supply prolongs S phase and induces G2 arrest.
• This arrest prevents entry into mitosis.

Conclusions:

• A novel cell cycle surveillance mechanism monitors nucleosome assembly.
• This mechanism operates independently of DNA repair pathways.
• It functions by suppressing CDC25 phosphatase (String) expression.