Phosphorylation of 'SDT-like' motifs in ATRX mediates its interaction with the MRN complex and is important for ALT...

Area of Science:

• Oncology
• Molecular Biology
• Genetics

Background:

• 10-15% of human cancers are telomerase-negative and utilize the alternative lengthening of telomeres (ALT) pathway.
• Loss of the alpha-thalassemia/mental retardation, X-linked (ATRX) chromatin remodeler is frequent in ALT-positive cancers but insufficient alone to induce ALT.
• The interaction between ATRX and the MRN complex, vital for ALT, was previously observed but lacked molecular detail.

Purpose of the Study:

• To elucidate the molecular mechanisms underlying the interaction between ATRX and the MRN complex.
• To investigate the role of specific ATRX domains and post-translational modifications in this interaction.
• To determine the functional significance of the ATRX-MRN interaction in preventing ALT pathway activation.

Main Methods:

• Investigated ATRX-MRN interaction using domain mapping of NBS1.
• Identified critical 'SDT-like' motifs in ATRX's central region.
• Utilized casein kinase 2 inhibition to assess the role of phosphorylation.
• Assessed ATRX's function in preventing ALT hallmarks in response to DNA-protein crosslinks.

Main Results:

• The ATRX-MRN interaction depends on NBS1's N-terminal forkhead-associated and BRCA1 C-terminal domains.
• Conserved 'SDT-like' motifs within ATRX's central unstructured region are essential for MRN binding.
• Casein kinase 2 inhibition disrupts ATRX-MRN binding, indicating phosphorylation is key.
• A functional ATRX-MRN interaction is necessary for ATRX to suppress ALT hallmarks induced by DNA-protein crosslinks.

Conclusions:

• The study defines the molecular basis of the ATRX-MRN interaction, involving specific NBS1 domains and phosphorylated ATRX motifs.
• This interaction is critical for ATRX's tumor-suppressive function against ALT pathway activation.
• Findings have implications for understanding ATR-X syndrome and developing targeted cancer therapies.