CDK phosphorylation of TRF2 controls t-loop dynamics during the cell cycle.

Area of Science:

• Molecular Biology
• Cell Biology
• Genetics

Background:

• Telomeres protect chromosome ends from DNA damage signaling and repair.
• Telomere loops (t-loops) are proposed structures that safeguard chromosome ends.
• Regulation of t-loop dynamics is crucial for telomere replication and maintenance.

Purpose of the Study:

• To investigate the regulation and physiological importance of t-loops in telomere protection.
• To identify the molecular mechanisms controlling t-loop assembly and disassembly.

Main Methods:

• Identification of a CDK phosphorylation site (Ser365) in TRF2.
• Investigated the role of PP6R3 phosphatase in TRF2 dephosphorylation during S phase.
• Examined the interaction between TRF2, RTEL1 helicase, and t-loops.

Main Results:

• TRF2 dephosphorylation at Ser365 by PP6R3 during S phase creates a window for RTEL1 to unwind t-loops, facilitating telomere replication.
• Re-phosphorylation of TRF2 outside of S phase releases RTEL1, protecting t-loops from unwinding and preventing ATM activation.
• This phospho-switch mechanism prevents replication conflicts and DNA damage responses within telomeres and the genome.

Conclusions:

• A TRF2 phospho-switch coordinates t-loop dynamics throughout the cell cycle.
• This regulation protects telomeres from replication stress and unscheduled DNA damage responses.
• The findings elucidate a novel mechanism for maintaining telomere integrity.