Yeast KEOPS complex regulates telomere length independently of its t⁶A modification function

Area of Science:

• Cell Biology
• Molecular Biology
• Genetics

Background:

• The KEOPS complex and Sua5 are conserved in Saccharomyces cerevisiae.
• These complexes are known to catalyze N⁶-threonylcarbamoyladenosine (t⁶A) tRNA modification.
• Their role in telomere replication and recombination is established, but the link to t⁶A modification is unclear.

Purpose of the Study:

• To investigate whether the telomere regulatory function of Sua5 and KEOPS depends on their t⁶A modification activity.
• To elucidate the mechanism by which KEOPS influences telomere length and structure.
• To determine if telomerase RNA TLC1 is a substrate for KEOPS.

Main Methods:

• Genetic analysis of KEOPS subunits and telomere length.
• Biochemical assays to assess t⁶A modification activity.
• In vivo and in vitro experiments to study telomere structure and G-overhangs.
• Mitochondrial Qri7 overexpression experiments.

Main Results:

• KEOPS and Sua5 regulate telomere length in a shared genetic pathway.
• KEOPS-mediated telomere length regulation is independent of its t⁶A biosynthesis activity.
• Overexpression of mitochondrial Qri7 rescues tRNA modification and growth but not telomere length in KEOPS mutants.
• Deletion of KEOPS subunits significantly reduces telomeric G-overhangs.
• Evidence suggests telomerase RNA TLC1 is not modified by KEOPS.

Conclusions:

• KEOPS regulates telomere replication through a mechanism independent of its tRNA modification function.
• KEOPS promotes telomere length maintenance by facilitating G-overhang generation.
• The study provides a model where KEOPS acts on telomere replication distinct from its role in tRNA modification.