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Highly conserved repetitive DNA sequences are present at human centromeres
D L Grady1, R L Ratliff, D L Robinson
1Center for Human Genome Studies, Los Alamos National Laboratory, University of California, NM 87545.
Summary
A conserved DNA sequence, (GGAAT)n, located in human centromeres, shares similarities with yeast centromeres. This finding suggests its potential role in the functional human centromere, supported by its unique properties and protein interactions.
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- Repetitive DNA sequences are crucial for genome organization and function.
- Human satellite DNA, including satellites II and III, contains highly conserved repetitive elements.
- The Saccharomyces cerevisiae centromere DNA element III (CDE III) is essential for yeast centromere function.
Purpose of the Study:
- To identify and characterize conserved repetitive DNA sequences in the human genome.
- To investigate the potential role of the (GGAAT)n sequence in human centromere function.
- To explore the biophysical and protein-binding properties of the (GGAAT)n sequence.
Main Methods:
- High-stringency hybridization using a human repetitive DNA library and rodent repetitive DNA probes.
- In situ hybridization to human and Drosophila chromosomes.
- Hyperchromicity studies on DNA sequences and variants.
- DNA-mobility-shift assays to assess protein binding affinity.
Main Results:
- Isolation of (GGAAT)n repeat clones, predominant in human satellites II and III.
- Localization of (GGAAT)n sequences to centromeric regions in human and Drosophila chromosomes.
- Unusual thermal stability of the purine-rich strand of (GGAAT)n, shared by (AATGN)n sequences.
- High-affinity binding of specific nuclear proteins to the (GGAAT)n sequence.
Conclusions:
- The (GGAAT)n sequence is highly conserved, centromerically located, and possesses unique biophysical properties.
- Its similarity to yeast centromeric DNA and high affinity for nuclear proteins suggest a role in the functional human centromere.
- This repetitive DNA sequence may represent a key component of the human centromere.