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Nucleolar localization of the human telomeric repeat binding factor 2 (TRF2).
Suisheng Zhang1, Peter Hemmerich, Frank Grosse
1Biochemistry, Institute of Molecular Biotechnology, PO Box 100 813, 07708 Jena, Germany.
Journal of Cell Science
|July 22, 2004
Summary
The telomeric repeat binding factor 2 (TRF2) is found in the nucleolus, not just telomeres. The nucleolus sequesters TRF2, impacting its telomere functions, especially during mitosis.
Area of Science:
- Cell Biology
- Molecular Biology
- Genetics
Background:
- Telomeric repeat binding factor 2 (TRF2) binds TTAGGG repeats at chromosome ends.
- TRF2's localization and function are crucial for telomere stability.
Purpose of the Study:
- To investigate the unexpected nucleolar localization of TRF2 in human cells.
- To understand the relationship between TRF2's nucleolar presence and its telomeric functions.
Main Methods:
- Immunofluorescence microscopy to visualize TRF2, UBF, and B23.
- Actinomycin D treatment to inhibit RNA polymerase I and observe protein relocalization.
- Analysis of TRF2 in nucleolar extracts and its DNA-binding complexes.
- Correlation of TRF2 localization with cell cycle progression and mitosis.
Main Results:
- TRF2 exhibits prominent nucleolar localization in discrete dots, separate from UBF and B23.
- TRF2 remains in the nucleolus upon RNA polymerase I inhibition, unlike UBF and B23.
- TRF2 localization varies with cell cycle: prominent in G0/S, reduced in G2, returns post-mitosis.
- Actinomycin D delays TRF2's release from the nucleolus during mitosis, correlating with chromosome end-to-end fusions.
Conclusions:
- The nucleolus acts as a reservoir for TRF2, influencing its availability at telomeres.
- TRF2's nucleolar sequestration impacts its role in maintaining telomere integrity, particularly under specific cellular conditions.