Role of the E3 ubiquitin ligase RNF157 as a novel downstream effector linking PI3K and MAPK signaling pathways to the cell cycle

J Biol Chem. 2017 Sep 1;292(35):14311-14324. doi: 10.1074/jbc.M117.792754. Epub 2017 Jun 27.


The interconnected PI3K and MAPK signaling pathways are commonly perturbed in cancer. Dual inhibition of these pathways by the small-molecule PI3K inhibitor pictilisib (GDC-0941) and the MEK inhibitor cobimetinib (GDC-0973) suppresses cell proliferation and induces cell death better than either single agent in several preclinical models. Using mass spectrometry-based phosphoproteomics, we have identified the RING finger E3 ubiquitin ligase RNF157 as a target at the intersection of PI3K and MAPK signaling. We demonstrate that RNF157 phosphorylation downstream of the PI3K and MAPK pathways influences the ubiquitination and stability of RNF157 during the cell cycle in an anaphase-promoting complex/cyclosome-CDH1-dependent manner. Deletion of these phosphorylation-targeted residues on RNF157 disrupts binding to CDH1 and protects RNF157 from ubiquitination and degradation. Expression of the cyclin-dependent kinase 2 (CDK2), itself a downstream target of PI3K/MAPK signaling, leads to increased phosphorylation of RNF157 on the same residues modulated by PI3K and MAPK signaling. Inhibition of PI3K and MEK in combination or of CDK2 by their respective small-molecule inhibitors reduces RNF157 phosphorylation at these residues and attenuates RNF157 interaction with CDH1 and its subsequent degradation. Knockdown of endogenous RNF157 in melanoma cells leads to late S phase and G2/M arrest and induces apoptosis, the latter further potentiated by concurrent PI3K/MEK inhibition, consistent with a role for RNF157 in the cell cycle. We propose that RNF157 serves as a novel node integrating oncogenic signaling pathways with the cell cycle machinery and promoting optimal cell cycle progression in transformed cells.

Keywords: CDK2; E3 ubiquitin ligase; MAPK; PIK3CA; cell cycle; cell signaling; cyclin; melanoma.

MeSH terms

  • Amino Acid Substitution
  • Antigens, CD
  • Apoptosis* / drug effects
  • Cadherins / antagonists & inhibitors
  • Cadherins / genetics
  • Cadherins / metabolism
  • Cell Line, Tumor
  • Cell Proliferation / drug effects
  • Cyclin-Dependent Kinase 2 / antagonists & inhibitors
  • Cyclin-Dependent Kinase 2 / genetics
  • Cyclin-Dependent Kinase 2 / metabolism
  • Enzyme Inhibitors / pharmacology
  • Enzyme Stability / drug effects
  • Gene Deletion
  • Gene Expression Regulation, Neoplastic / drug effects
  • Humans
  • MAP Kinase Signaling System* / drug effects
  • Melanoma / drug therapy
  • Melanoma / enzymology
  • Melanoma / metabolism*
  • Melanoma / pathology
  • Neoplasm Proteins / antagonists & inhibitors
  • Neoplasm Proteins / chemistry
  • Neoplasm Proteins / genetics
  • Neoplasm Proteins / metabolism
  • Phosphatidylinositol 3-Kinase / metabolism*
  • Phosphoinositide-3 Kinase Inhibitors
  • Phosphorylation / drug effects
  • Point Mutation
  • Protein Processing, Post-Translational* / drug effects
  • RNA Interference
  • Recombinant Fusion Proteins / chemistry
  • Recombinant Fusion Proteins / metabolism
  • S Phase / drug effects
  • Signal Transduction* / drug effects
  • Ubiquitin-Protein Ligases / antagonists & inhibitors
  • Ubiquitin-Protein Ligases / chemistry
  • Ubiquitin-Protein Ligases / genetics
  • Ubiquitin-Protein Ligases / metabolism*
  • Ubiquitination / drug effects


  • Antigens, CD
  • CDH1 protein, human
  • Cadherins
  • Enzyme Inhibitors
  • Neoplasm Proteins
  • Phosphoinositide-3 Kinase Inhibitors
  • Recombinant Fusion Proteins
  • RNF157 protein, human
  • Ubiquitin-Protein Ligases
  • Phosphatidylinositol 3-Kinase
  • CDK2 protein, human
  • Cyclin-Dependent Kinase 2