The Tetrahymena telomerase p75-p45-p19 subcomplex is a unique CST complex

Area of Science:

• Molecular Biology
• Biochemistry
• Genetics

Background:

• The Tetrahymena telomerase holoenzyme includes subunits p75, p45, and p19, forming a peripheral subcomplex (7-4-1).
• The CST (CTC1-Stn1-Ten1) complex is known to stimulate telomerase activity in other organisms.

Purpose of the Study:

• To determine the structures of p45 and p19 subunits from Tetrahymena.
• To elucidate the role of the 7-4-1 subcomplex in telomere maintenance.

Main Methods:

• X-ray crystallography to determine the structures of p45 and p19.
• Biochemical assays to assess the function of the 7-4-1 subcomplex.
• Genetic manipulation (mutant p19 overexpression) to study telomere dynamics.

Main Results:

• The structures of p45 and p19 were determined, identifying them as the Stn1 and Ten1 subunits of the CST complex.
• The 7-4-1 subcomplex binds telomeric single-stranded DNA.
• Overexpression of a mutant p19 subunit leads to the elongation of telomere 3'-overhangs.

Conclusions:

• Tetrahymena CST complex, composed of p75, p45 (Stn1), and p19 (Ten1), is a component of the telomerase holoenzyme.
• Telomerase-tethered Tetrahymena CST plays a role in coordinating telomere G-strand and C-strand synthesis.
• The CST complex's interaction with telomeric DNA influences telomere length regulation.