Nucleolar organization as revealed in cycloheximide treated cells

Area of Science:

• Cell Biology
• Molecular Biology
• Biochemistry

Background:

• The nucleolus is a key cellular organelle involved in ribosome biogenesis and other functions.
• Understanding nucleolar organization is crucial for comprehending cellular processes and responses to stress.

Purpose of the Study:

• To investigate the dynamic changes in nucleolar organization in response to cycloheximide treatment.
• To characterize the structural components of the nucleolus, specifically the nucleolonemal network and granules.

Main Methods:

• Treatment of rat kangaroo cells with cycloheximide.
• Microscopic observation of nucleolar morphology.
• Analysis of nucleolar structural components and their relationship to rDNA transcriptional units.

Main Results:

• Cycloheximide treatment induced a transition from dense nucleoli to a looser structure with a prominent nucleolonemal network within 1 hour.
• Extended treatment led to scarce granules and a more defined nucleolonemal network, with units comparable in length to rDNA transcriptional units.
• The nucleolonemal network appeared composed of fibril tufts.
• Upon cycloheximide withdrawal, granules reappeared and obscured the nucleolonemal network.

Conclusions:

• Cycloheximide treatment reversibly alters nucleolar organization, highlighting the dynamic nature of this organelle.
• The nucleolonemal network is a significant structural feature of the nucleolus, potentially related to active transcription.
• Granules and the nucleolonemal network represent distinct, interconvertible states of nucleolar organization.