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Histone H4 mRNA is stored as a small cytoplasmic RNP during the G2 phase in Physarum polycephalum
M L Wilhelm1, B Toublan, R A Fujita
1Institut de Biologie Moléculaire et Cellulaire du CNRS, Strasbourg, France.
Biochemical and Biophysical Research Communications
|May 31, 1988
Summary
Histone H4 gene transcription in Physarum polycephalum peaks during G2 phase. Stored H4 mRNA in the cytoplasm is later translated during the subsequent S phase, ensuring protein availability.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Histone H4 is crucial for DNA packaging and replication.
- Gene transcription regulation is vital for cell cycle progression.
Purpose of the Study:
- To investigate the temporal regulation of histone H4 gene transcription in Physarum polycephalum.
- To understand the storage and activation mechanisms of histone H4 mRNA during the cell cycle.
Main Methods:
- In vivo pulse-labeling experiments to measure mRNA synthesis rates.
- Sucrose gradient fractionation of cytoplasmic ribonucleoprotein (RNP) complexes.
- Blot hybridization for subcellular fraction analysis.
Main Results:
- Histone H4 gene transcription significantly increases during the G2 phase, peaking at the end of G2.
- H4 mRNA accumulates in the cytoplasm during G2 but remains untranslated.
- Stored H4 mRNA is stabilized as an inactive mRNP complex until the S phase.
Conclusions:
- Histone H4 gene transcription is tightly regulated, occurring primarily during the G2 phase.
- Physarum polycephalum employs a post-transcriptional regulatory mechanism, storing H4 mRNA for timely protein production during S phase.
- Cytoplasmic RNP complex formation is key to stabilizing and storing H4 mRNA.