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Long telomeric C-rich 5'-tails in human replicating cells
Graziella Cimino-Reale1, Esterina Pascale, Ester Alvino
1Istituto di Neurobiologia e Medicina Molecolare, Consiglio Nazionale delle Ricerche, 00137 Roma, Italy.
The Journal of Biological Chemistry
|November 19, 2002
Summary
Telomere replication models suggest blunt ends, but this study reveals C-rich 5' tails. Inefficient leading-strand synthesis may drive telomere shortening in proliferating cells.
Area of Science:
- Molecular Biology
- Genetics
- Cell Biology
Background:
- Telomeres protect chromosome ends from degradation and recombination.
- Replication models predict blunt ends and G-rich 3' overhangs, but experimental data show discrepancies.
- Human telomeres exhibit long G-rich 3' overhangs, with blunt end persistence being uncertain.
Purpose of the Study:
- To investigate the nature of DNA ends after leading-strand telomere synthesis.
- To determine if C-rich 5' tails are present and their relation to cell proliferation.
- To re-evaluate models of telomere replication and their impact on telomere length.
Main Methods:
- Analysis of single-stranded G-rich and C-rich DNA in human fibroblasts and HeLa cells.
- Examination of telomere structures in proliferating and telomerase-negative cells.
- Correlation analysis between 5' C-rich tail characteristics and cell proliferation rates.
Main Results:
- Leading-strand synthesis can produce C-rich 5' tails, not always blunt ends.
- 5' overhangs were predominantly observed during the S phase of the cell cycle.
- The quantity and length of 5' C-rich tails correlated significantly with cellular proliferation rates.
Conclusions:
- Leading-strand DNA synthesis at telomeres is inefficient.
- The formation of C-rich 5' tails contributes to telomere shortening.
- Current telomere replication models may need revision to account for these findings.