Cell-cycle-regulated association of RAD50/MRE11/NBS1 with TRF2 and human telomeres

Area of Science:

• Molecular Biology
• Cell Biology
• Genetics

Background:

• Telomeres protect chromosome ends from degradation and fusion.
• Telomere protection in human cells relies on TRF2, which may form t-loops.
• The function of TRF2 in DNA double-strand break (DSB) repair is unclear.

Purpose of the Study:

• To investigate the association of the MRE11 complex with TRF2 at human telomeres.
• To determine the role of TRF2 and the MRE11 complex in response to DNA damage.

Main Methods:

• Nanoelectrospray tandem mass spectrometry to identify proteins in TRF2 immunocomplexes.
• Protein blotting to confirm the association of RAD50, MRE11, and NBS1 with TRF2.
• Indirect immunofluorescence to visualize protein localization at telomeres and in response to irradiation.

Main Results:

• RAD50, MRE11, and NBS1 were found to be associated with TRF2 in human cells.
• RAD50 and MRE11 localize to interphase telomeres.
• NBS1 associates with TRF2 and telomeres during S phase.
• TRF2 does not relocate to irradiation-induced foci, and its association with the MRE11 complex is unaffected by irradiation.

Conclusions:

• The MRE11 complex is present at human telomeres and associated with TRF2.
• TRF2 is unlikely to be involved in direct double-strand break repair.
• The MRE11 complex may play a role in telomere maintenance, potentially by modulating t-loop formation by TRF2.