Sequence-specific and 3'-end selective single-strand DNA binding by the Oxytricha nova telomere end binding protein...

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• Telomeres protect chromosome ends from degradation.
• Oxytricha nova telomere end binding protein (OnTEBP) recognizes specific telomeric DNA sequences.
• Homologs of OnTEBP are found across eukaryotes, suggesting conserved functions.

Purpose of the Study:

• To investigate the sequence specificity and 3"-end selectivity of OnTEBP alpha subunit binding to telomeric DNA.
• To compare binding affinities based on nucleotide substitutions and additions at the telomere repeat.
• To gain insights into the mechanisms of single-stranded DNA recognition by proteins.

Main Methods:

• Comparative binding studies using the N-terminal domain of the OnTEBP alpha subunit.
• Analysis of binding affinity with modified telomeric DNA sequences (additions and substitutions).
• Integration of structural and binding data.

Main Results:

• OnTEBP binding affinity is modestly reduced (up to 7-fold) by nucleotides added to the 3"-end of the telomere repeat.
• Specific base substitutions within the telomeric repeat significantly impact binding affinity, with some causing minimal change and others a >20-fold decrease.
• The study identified critical bases within the telomeric repeat essential for high-affinity binding.

Conclusions:

• OnTEBP exhibits specificity for the 3"-terminus of telomeric DNA.
• The binding affinity is highly sensitive to specific nucleotide sequences within the telomeric repeat.
• Structural and binding data provide a detailed understanding of ssDNA recognition mechanisms.