Related Experiment Video
Updated: Aug 13, 2026
08:49
Peering at Brain Polysomes with Atomic Force Microscopy
Published on: March 16, 2016
Ribosomal gene transcription is organized in foci within nucleolar components
W Mosgoeller1, C Schöfer, J Wesierska-Gadek
1Institute of Histology and Embryology, University of Vienna, Wien, Austria.
Histochemistry and Cell Biology
|March 21, 1998
Summary
This study reveals that specific nucleolar components manage ribosome biogenesis. Transcription proteins and nascent RNA localize to distinct regions within the dense fibrillar component, indicating functional subcompartmentalization.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Ribosome biogenesis is crucial for cell function.
- The nucleolus is the primary site of ribosome biogenesis.
- Understanding the spatial organization of nucleolar components is key to deciphering its functions.
Purpose of the Study:
- To investigate the role of nucleolar components in ribosome biogenesis.
- To map ribosomal DNA (rDNA) transcription loci within the nucleolus.
- To analyze the ultrastructural distribution of transcription-associated proteins and nascent transcripts.
Main Methods:
- In situ transcription assays (non-autoradiographic).
- Immunological analysis of transcription-associated proteins (polymerase I, upstream binding factor, topoisomerase I).
- Visualization of nascent transcripts via bromouridine incorporation.
Main Results:
- Transcription proteins were found in the fibrillar center and dense fibrillar component (DF) of nucleoli.
- Nascent transcripts colocalized with transcription proteins in specific regions of the DF.
- No colocalization of rDNA with nascent transcripts was observed in the fibrillar centers, suggesting inactivity.
Conclusions:
- Ribosomal DNA transcription is confined to small foci within the nucleolus.
- The dense fibrillar component (DF) exhibits functional subcompartmentalization.
- Only a minor portion of the DF is actively involved in transcription.
Related Concept Videos
01:27Ribosomes
Ribosomes translate genetic information encoded by messenger RNA (mRNA) into proteins. Both prokaryotic and eukaryotic cells have ribosomes. Cells that synthesize large quantities of protein—such as secretory cells in the human pancreas—can contain millions of ribosomes.Ribosome Structure and AssemblyRibosomes are composed of ribosomal RNA (rRNA) and proteins. In eukaryotes, rRNA is transcribed from genes in the nucleolus—a part of the nucleus that specializes in ribosome production. Within the...
02:53Ribosomal RNA Synthesis
Ribosome synthesis is a highly complex and coordinated process involving more than 200 assembly factors. The synthesis and processing of ribosomal components occurs not only in the nucleolus but also in the nucleoplasm and the cytoplasm of eukaryotic cells.
Ribosome biogenesis begins with the synthesis of 5S and 45S pre-rRNAs by distinct RNA polymerases. The primary transcripts are extensively processed and modified before they are bound and folded by ribosomal proteins and assembly factors,...
Ribosome biogenesis begins with the synthesis of 5S and 45S pre-rRNAs by distinct RNA polymerases. The primary transcripts are extensively processed and modified before they are bound and folded by ribosomal proteins and assembly factors,...
02:55The Nucleolus
The nucleolus is the most prominent substructure of the nucleus. When it was first discovered, it was considered to be an isolated organelle that forms fibrils and granules. In 1931, the relationship between the nucleolus and chromosomes was first described by Heitz. He observed that the appearance and size of nucleolus varies depending on the stage of the cell cycle. He also noticed constricted regions on different chromosomes clustered together at definite cell cycle stages. These regions,...
02:53Ribosomal RNA Synthesis
Ribosome synthesis is a highly complex and coordinated process involving more than 200 assembly factors. The synthesis and processing of ribosomal components occurs not only in the nucleolus but also in the nucleoplasm and the cytoplasm of eukaryotic cells.
Ribosome biogenesis begins with the synthesis of 5S and 45S pre-rRNAs by distinct RNA polymerases. The primary transcripts are extensively processed and modified before they are bound and folded by ribosomal proteins and assembly factors,...
Ribosome biogenesis begins with the synthesis of 5S and 45S pre-rRNAs by distinct RNA polymerases. The primary transcripts are extensively processed and modified before they are bound and folded by ribosomal proteins and assembly factors,...
02:55The Nucleolus
The nucleolus is the most prominent substructure of the nucleus. When it was first discovered, it was considered to be an isolated organelle that forms fibrils and granules. In 1931, the relationship between the nucleolus and chromosomes was first described by Heitz. He observed that the appearance and size of nucleolus varies depending on the stage of the cell cycle. He also noticed constricted regions on different chromosomes clustered together at definite cell cycle stages. These regions,...
01:27Ribosomes
Ribosomes translate genetic information encoded by messenger RNA (mRNA) into proteins. Both prokaryotic and eukaryotic cells have ribosomes. Cells that synthesize large quantities of protein—such as secretory cells in the human pancreas—can contain millions of ribosomes.
Ribosome Structure and Assembly
Ribosomes are composed of ribosomal RNA (rRNA) and proteins. In eukaryotes, rRNA is transcribed from genes in the nucleolus—a part of the nucleus that specializes in ribosome production. Within...
Ribosome Structure and Assembly
Ribosomes are composed of ribosomal RNA (rRNA) and proteins. In eukaryotes, rRNA is transcribed from genes in the nucleolus—a part of the nucleus that specializes in ribosome production. Within...