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Relationship between the number and function of human ribosomal genes
A de Capoa1, M P Felli, A Baldini
1Dipartimento di Genetica e Biologia Molecolare, Università La Sapienza, Rome, Italy.
Human Genetics
|August 1, 1988
Summary
The number of ribosomal RNA genes doesn't always correlate with their activity. Gene expression levels depend on factors beyond just gene copy number, impacting ribosomal RNA gene regulation.
Area of Science:
- Molecular Biology
- Genetics
- Cell Biology
Background:
- Ribosomal RNA (rRNA) genes are crucial for protein synthesis.
- The acrocentric chromosomes (13, 14, 15, 21, 22) contain rRNA gene clusters.
- Understanding the relationship between rRNA gene copy number and activity is vital for cellular function.
Purpose of the Study:
- To investigate the correlation between the number of ribosomal RNA genes and their transcriptional activity.
- To analyze rRNA gene expression across different human cell types.
- To identify factors influencing rRNA gene cluster expression levels.
Main Methods:
- Quantified rRNA gene copy number using in situ hybridization with 3H-labeled human 18S rDNA on metaphase chromosomes.
- Assessed rRNA gene activity by silver staining nucleolus organizer regions (NORs), measuring NOR size, and analyzing satellite association frequency.
- Evaluated results across phytohemagglutinin-stimulated T-lymphocytes, Epstein-Barr virus transformed lymphoblasts, and fibroblasts.
Main Results:
- Chromosome 21 showed few gene copies and low activity.
- Chromosome 22 had numerous gene copies but exhibited low activity.
- Both chromosomes 14 possessed few gene copies yet demonstrated high activity.
Conclusions:
- Ribosomal RNA gene copy number is not the sole determinant of gene expression.
- Factors other than gene quantity significantly influence the expression level of rRNA gene clusters.
- The regulation of rRNA gene activity is complex and multifactorial.