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Published on: June 9, 2017
DNA Damage Regulates the Functions of the RNA Binding Protein Sam68 through ATM-Dependent Phosphorylation
Venturina Stagni1,2, Silvia Orecchia2, Luca Mignini3
1Institute of Molecular Biology and Pathology, National Research Council (CNR), 00185 Rome, Italy.
Abstract:
Cancer cells frequently exhibit dysregulation of the DNA damage response (DDR), genomic instability, and altered RNA metabolism. Recent genome-wide studies have strongly suggested an interaction between the pathways involved in the cellular response to DDR and in the regulation of RNA metabolism, but the molecular mechanism(s) involved in this crosstalk are largely unknown. Herein, we found that activation of the DDR kinase ATM promotes its interaction with Sam68, leading to phosphorylation of this multifunctional RNA binding protein (RBP) on three residues: threonine 61, serine 388 and serine 390. Moreover, we demonstrate that ATM-dependent phosphorylation of threonine 61 promotes the function of Sam68 in the DDR pathway and enhances its RNA processing activity. Importantly, ATM-mediated phosphorylation of Sam68 in prostate cancer cells modulates alternative polyadenylation of transcripts that are targets of Sam68, supporting the notion that the ATM-Sam68 axis exerts a multifaceted role in the response to DNA damage. Thus, our work validates Sam68 as an ATM kinase substrate and uncovers an unexpected bidirectional interplay between ATM and Sam68, which couples the DDR pathway to modulation of RNA metabolism in response to genotoxic stress.
Insights
The DNA damage response kinase ATM phosphorylates RNA-binding protein Sam68, enhancing its role in DNA repair and RNA processing. This ATM-Sam68 interaction links DNA damage response pathways to RNA metabolism regulation.
Area of Science:
- Molecular biology
- Cancer research
- Genetics
Background:
- Cancer cells often show dysregulated DNA damage response (DDR), genomic instability, and altered RNA metabolism.
- The molecular mechanisms connecting DDR and RNA metabolism pathways are not well understood.
Purpose of the Study:
- To investigate the crosstalk between the DNA damage response kinase ATM and RNA metabolism.
- To identify the role of Sam68, a multifunctional RNA binding protein (RBP), in this crosstalk.
Main Methods:
- Investigated the interaction between ATM and Sam68 using biochemical assays.
- Analyzed ATM-dependent phosphorylation of Sam68 on specific residues.
- Assessed the impact of Sam68 phosphorylation on its function in DDR and RNA processing.
- Examined alternative polyadenylation of Sam68 target transcripts in prostate cancer cells.
Main Results:
- Activation of ATM leads to its interaction with Sam68.
- ATM phosphorylates Sam68 on threonine 61, serine 388, and serine 390.
- Phosphorylation of threonine 61 enhances Sam68's function in DDR and RNA processing.
- ATM-mediated Sam68 phosphorylation influences alternative polyadenylation of target transcripts in prostate cancer.
Conclusions:
- Sam68 is a substrate for the ATM kinase.
- An ATM-Sam68 axis couples DDR to RNA metabolism modulation.
- This interplay plays a multifaceted role in cellular responses to genotoxic stress.
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