Npl3 stabilizes R-loops at telomeres to prevent accelerated replicative senescence

Area of Science:

• Molecular Biology
• Cell Biology
• Genetics

Background:

• Telomere shortening is a critical factor in cellular aging and replicative senescence.
• Telomeric repeat-containing RNA (TERRA) R-loops are known to stabilize critically short telomeres.
• Homology-directed repair (HDR) is a mechanism that can elongate telomeres.

Purpose of the Study:

• To identify novel factors that bind to telomeres and regulate telomere length.
• To investigate the role of the RNA-binding protein Npl3 in telomere maintenance.
• To elucidate the mechanism by which TERRA R-loops influence telomere elongation and senescence.

Main Methods:

• Non-bias proteomic approach to identify telomere binding factors.
• Chromatin immunoprecipitation (ChIP) and RNA immunoprecipitation (RIP) to detect molecular interactions.
• Genetic and biochemical assays to study protein-RNA and protein-DNA interactions.

Main Results:

• Npl3 was identified as a novel telomere binding factor.
• Npl3 directly interacts with TERRA and telomeres.
• Npl3 associates with telomeres in an R-loop-dependent manner, stabilizing R-loops at short telomeres.
• Npl3 promotes HDR-mediated telomere elongation and prevents premature replicative senescence.

Conclusions:

• Npl3 is a key regulator of telomere length maintenance by stabilizing TERRA R-loops at short telomeres.
• The Npl3-TERRA R-loop interaction promotes HDR, counteracting senescence.
• Dysregulation of this pathway may contribute to diseases associated with excessive telomere shortening.