Notch-induced E2A ubiquitination and degradation are controlled by MAP kinase activities.
Notch signals are important for lymphocyte development but downstream events that follow Notch signaling are not well understood. Here, we report that signaling through Notch modulates the turnover of E2A proteins including E12 and E47, which are basic helix-loop-helix proteins crucial for B and T lymphocyte development. Notch-induced degradation requires phosphorylation of E47 by p42/p44 MAP kinases. Expression of the intracellular domain of Notch1 (N1-IC) enhances the association of E47 with the SCF(Skp2) E3 ubiquitin ligase and ubiquitination of E47, followed by proteasome-mediated degradation. Furthermore, N1-IC induces E2A degradation in B and T cells in the presence of activated MAP kinases. Activation of endogenous Notch receptors by treatment of splenocytes with anti-IgM or anti-CD3 plus anti-CD28 also leads to E2A degradation, which is blocked by the inhibitors of Notch activation or proteasome function. Notch-induced E2A degradation depends on the function of its downstream effector, RBP-Jkappa, probably to activate target genes involved in the ubiquitination of E2A proteins. Thus we propose that Notch regulates lymphocyte differentiation by controlling E2A protein turnover.
Immunobiology and Cancer Program, Oklahoma Medical Research Foundation, 825 NE 13th Street, Oklahoma City, OK 73104, USA.
Lei
L
Nie
Min
M
Xu
Antoaneta
A
Vladimirova
Xiao-Hong
XH
Sun
D000818:Animals; D001402:B-Lymphocytes / Q000378:metabolism; D001483:Base Sequence; D051792:Basic Helix-Loop-Helix Proteins; D001665:Binding Sites; D002460:Cell Line; D018076:DNA, Complementary / Q000235:genetics; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism*; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D008954:Models, Biological; D041681:NIH 3T3 Cells; D010766:Phosphorylation; D017434:Protein Structure, Tertiary; D051881:Receptor, Notch1; D011956:Receptors, Cell Surface; D017384:Sequence Deletion; D015398:Signal Transduction; D013601:T-Lymphocytes / Q000378:metabolism; D051820:TCF Transcription Factors; D058125:Transcription Factor 7-Like 1 Protein; D014157:Transcription Factors / Q000378:metabolism*; D025801:Ubiquitin / Q000378:metabolism
D051792:Basic Helix-Loop-Helix Proteins; D018076:DNA, Complementary; D004268:DNA-Binding Proteins; D008565:Membrane Proteins; D020928:Mitogen-Activated Protein Kinases; D051881:Receptor, Notch1; D011956:Receptors, Cell Surface; D051820:TCF Transcription Factors; D058125:Transcription Factor 7-Like 1 Protein; D014157:Transcription Factors; D025801:Ubiquitin; C497762:Notch1 protein, mouse; C407909:TCF3 protein, human; C544912:TCF7L1 protein, human; C544913:Tcf7l1 protein, mouse