DNA recognition and binding by the Euplotes telomere protein.

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• Telomeres protect chromosome ends from degradation.
• Euplotes crassus telomeres consist of C4A4.T4G4 repeats.
• Telomere-binding proteins are essential for telomere maintenance.

Purpose of the Study:

• To investigate the DNA-binding specificity of the Euplotes crassus 51-kDa telomere protein.
• To identify the DNA-binding domain of the telomere protein.

Main Methods:

• Purified telomere protein was tested for binding to various synthetic oligonucleotide sequences.
• Proteolytic digestion (trypsin) was used to identify protein domains.
• DNA-binding assays were performed under high salt conditions (2 M KCl).

Main Results:

• The 51-kDa protein specifically binds to the 3' terminus of single-stranded (T4G4)n DNA repeats.
• Binding is sequence- and structure-specific, with minimal tolerance for sequence variation.
• A 35-kDa N-terminal fragment retains high-affinity binding to single-stranded telomeric DNA.
• The C-terminal region influences terminus-specific binding.

Conclusions:

• The N-terminal 35-kDa domain of the Euplotes crassus telomere protein is responsible for specific DNA binding.
• The protein recognizes both sequence and structure of single-stranded telomeric DNA.
• The C-terminal portion contributes to the precise localization of binding to telomere termini.