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Hierarchical phosphorylation within the ankyrin repeat domain defines a phosphoregulatory loop that regulates Notch

Prathibha Ranganathan1, Rodrigo Vasquez-Del Carpio1, Fred M Kaplan1

  • 1Molecular Oncology Program, Division of Surgical Oncology, Dewitt Daughtry Family of Surgery and Sylvester Comprehensive Cancer Center, Miller School of Medicine, University of Miami, Miami Florida 33136.

The Journal of Biological Chemistry
|June 21, 2011
PubMed

Insights

Casein kinase 2 (CK2) phosphorylates Notch, a key signaling pathway protein. This phosphorylation reduces Notch transcriptional activity by disrupting its DNA binding, revealing a new regulatory mechanism.

Area of Science:

  • Cellular signaling
  • Molecular biology
  • Cancer research

Background:

  • The Notch pathway is crucial for cell communication and function.
  • Notch pathway dysregulation is implicated in human cancers.
  • Casein kinase 2 (CK2) is a kinase regulating various cellular processes.

Purpose of the Study:

  • To identify novel targets of CK2 phosphorylation.
  • To investigate the role of CK2 in regulating Notch signal transduction.
  • To elucidate the functional consequences of Notch phosphorylation by CK2.

Main Methods:

  • Phosphorylation site mapping and mutational analysis to identify target amino acids.
  • Biochemical assays to study protein complex formation and DNA binding.
  • Assessment of transcriptional activity following phosphorylation.

Main Results:

  • Notch intracellular domain (Notch ICD) is identified as a novel substrate for CK2.
  • Serine 1901 in the ankyrin domain of Notch is phosphorylated by CK2, creating a secondary site at threonine 1898.
  • Phosphorylation at both serine 1901 and threonine 1898 decreases the binding of the Notch-Mastermind-CSL complex to DNA, reducing transcriptional activity.

Conclusions:

  • CK2-mediated phosphorylation of Notch at serine 1901 and threonine 1898 negatively regulates Notch transcriptional activity.
  • This phosphorylation event impacts Notch function by promoting the dissociation of the Notch-Mastermind-CSL complex from DNA.
  • The study reveals a new regulatory mechanism for the essential Notch signaling pathway, highlighting the importance of precise control over its activity.

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