Arginine methylation regulates telomere length and stability

Area of Science:

• Molecular biology
• Cell biology
• Genetics

Background:

• Telomeres are crucial for chromosome stability and are protected by the shelterin complex, including TRF2.
• The N-terminal basic domain of TRF2 contains arginine residues, similar to motifs methylated by protein arginine methyltransferases (PRMTs).
• The role of arginine methylation in regulating TRF2 function and telomere maintenance remains largely unknown.

Purpose of the Study:

• To investigate the role of arginine methylation in TRF2 function.
• To determine if PRMT1 interacts with and methylates TRF2.
• To elucidate the impact of PRMT1-mediated TRF2 methylation on telomere stability and cell proliferation.

Main Methods:

• Site-directed mutagenesis of TRF2 arginines to lysines.
• Telomere dysfunction-induced focus (TIF) formation assays.
• Cellular senescence assays.
• Co-immunoprecipitation assays to assess protein interactions.
• In vitro and in vivo methylation assays.
• PRMT1 depletion studies using siRNA.
• Analysis of telomere length and stability (telomere doublets).
• Cell proliferation assays.

Main Results:

• TRF2 mutants with arginine-to-lysine substitutions in the basic domain induced TIFs and cellular senescence.
• Overexpression of TRF2 lysine mutants led to telomere instability, evidenced by accumulated telomere doublets.
• TRF2 directly interacts with PRMT1, and its basic domain arginines are methylated by PRMT1 both in vitro and in vivo.
• Loss of PRMT1 caused growth arrest in normal human cells but did not affect cancer cell proliferation.
• Depletion of PRMT1 in normal cells resulted in telomere doublets, similar to TRF2 lysine mutants.
• PRMT1 knockdown in cancer cells increased TRF2 association with telomeres, leading to telomere shortening.

Conclusions:

• Arginine methylation of TRF2 by PRMT1 is essential for maintaining telomere stability and preventing cellular senescence.
• PRMT1 plays a cell type-specific role in regulating cell proliferation, potentially through TRF2 methylation.
• Dysregulation of PRMT1-mediated TRF2 methylation contributes to telomere instability and may influence cancer cell behavior.