Structure of the human telomeric Stn1-Ten1 capping complex

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• The identification of the human CST complex (Cdc13-Stn1-Ten1) in 2009 presented new questions about telomere capping in eukaryotes.
• Understanding the structure and function of CST is crucial for comprehending telomere maintenance and genome stability.

Purpose of the Study:

• To elucidate the high-resolution structure of the human Stn1-Ten1 (hStn1-Ten1) complex.
• To investigate the functional significance of the hStn1-Ten1 interaction in telomere maintenance and protection.

Main Methods:

• X-ray crystallography was used to determine the high-resolution structure of the hStn1-Ten1 complex.
• Biochemical assays were performed to assess the DNA binding activity of the complex.
• Cell-based assays using hStn1 mutants were conducted to evaluate telomere length and stability.

Main Results:

• The structure revealed conserved domains in hStn1 and hTen1, similar to yeast and RPA complexes.
• The hStn1-Ten1 complex demonstrated non-specific single-stranded DNA binding activity, mainly dependent on hStn1.
• Mutants affecting hStn1-Ten1 dimerization led to telomere elongation and uncapping, highlighting hTen1's role.

Conclusions:

• The structural organization of the hStn1-Ten1 subcomplex is conserved across species.
• hTen1 is essential for the telomeric functions of the human CST complex, including telomere protection and telomerase regulation.