G-overhang dynamics at Tetrahymena telomeres

Area of Science:

• Molecular Biology
• Genetics
• Cell Biology

Background:

• Telomeres protect chromosome ends from degradation and fusion.
• The G-rich strand overhang at telomeres plays a crucial role in telomere maintenance and replication.
• Understanding telomere structure is vital for comprehending genome stability and aging.

Purpose of the Study:

• To precisely measure the length of the G-strand overhang at Tetrahymena thermophila telomeres.
• To investigate the regulation of telomere overhang structure during the cell cycle.
• To explore the presence and implications of overhangs in rDNA molecules.

Main Methods:

• Ligation-mediated primer extension protocol for accurate overhang length measurement.
• Analysis of telomere structure across different cell cycle stages.
• Cloning of rDNA molecules dependent on telomeric overhangs.

Main Results:

• Telomere G-strand overhang length and terminal nucleotide are tightly regulated, predominantly terminating in 5 -TTGGGGT.
• >80% of overhangs are 14-15 or 20-21 nucleotides long.
• Overhang length is stable during the cell cycle but changes upon cell cycle exit, indicating altered DNA processing or end protection.

Conclusions:

• Telomere G-strand overhang generation is a highly regulated process involving multiple DNA-processing events.
• rDNA molecules possess overhangs at both telomeres, enabling cloning strategies.
• A significant fraction of leading strand telomeres exhibit overhangs of at least 5 nucleotides.