Notch inhibition of E47 supports the existence of a novel signaling pathway.
E47 is a widely expressed transcription factor that activates B-cell-specific immunoglobulin gene transcription and is required for early B-cell development. In an effort to identify processes that regulate E47, and potentially B-cell development, we found that activated Notch1 and Notch2 effectively inhibit E47 activity. Only the intact E47 protein was inhibited by Notch-fusion proteins containing isolated DNA binding and activation domains were unaffected-suggesting that Notch targets an atypical E47 cofactor. Although overexpression of the coactivator p300 partially reversed E47 inhibition, results of several assays indicated that p300/CBP is not a general target of Notch. Notch inhibition of E47 did not correlate with its ability to activate CBF1/RBP-Jkappa, the mammalian homolog of Suppressor of Hairless, a protein that associates physically with Notch and defines the only known Notch signaling pathway in drosophila. Importantly, E47 was inhibited independently of CBF1/RPB-Jkappa by Deltex, a second Notch-interacting protein. We provide evidence that Notch and Deltex may act on E47 by inhibiting signaling through Ras because (i) full E47 activity was found to be dependent on Ras and (ii) both Notch and Deltex inhibited GAL4-Jun, a hybrid transcription factor whose activity is dependent on signaling from Ras to SAPK/JNK.
Ordentlich
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P
Howard Hughes Medical Institute and Department of Genetics, University of Pennsylvania School of Medicine, Philadelphia 19104-6145, USA.
Lin
A
A
Shen
C P
CP
Blaumueller
C
C
Matsuno
K
K
Artavanis-Tsakonas
S
S
Kadesch
T
T
D016475:3T3 Cells; D000818:Animals; D050882:CREB-Binding Protein; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D029721:Drosophila Proteins; D050881:E1A-Associated p300 Protein; D019476:Insect Proteins / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism*; D051379:Mice; D009687:Nuclear Proteins / Q000378:metabolism; D051881:Receptor, Notch1; D051883:Receptor, Notch2; D011956:Receptors, Cell Surface / Q000378:metabolism*; D012097:Repressor Proteins / Q000378:metabolism; D015398:Signal Transduction; D051820:TCF Transcription Factors; D015534:Trans-Activators; D058125:Transcription Factor 7-Like 1 Protein; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic; D018631:ras Proteins / Q000378:metabolism
D004268:DNA-Binding Proteins; C086679:DX protein, Drosophila; D029721:Drosophila Proteins; D019476:Insect Proteins; D008565:Membrane Proteins; C497762:Notch1 protein, mouse; C497765:Notch2 protein, mouse; D009687:Nuclear Proteins; D051881:Receptor, Notch1; D051883:Receptor, Notch2; D011956:Receptors, Cell Surface; D012097:Repressor Proteins; C088731:Su(H) protein, Drosophila; D051820:TCF Transcription Factors; C544913:Tcf7l1 protein, mouse; D015534:Trans-Activators; D058125:Transcription Factor 7-Like 1 Protein; D014157:Transcription Factors; D050882:CREB-Binding Protein; C494364:Crebbp protein, mouse; D050881:E1A-Associated p300 Protein; C494361:Ep300 protein, mouse; D018631:ras Proteins