Activated Notch1 modulates gene expression in B cells similarly to Epstein-Barr viral nuclear antigen 2.
Both Epstein-Barr viral nuclear antigen 2 (EBNA2) and activated Notch transactivate genes by interacting with the transcription factor RBP-Jkappa. The viral protein EBNA2 may hence be regarded as a functional equivalent of an activated Notch receptor. Until now, nothing has been known about the physiological role of Notch signaling in B cells. Here we investigated whether activated Notch can induce the same phenotypic changes as EBNA2 in Burkitt's lymphoma cells. An estrogen receptor fusion protein of the intracellular part of mouse Notch 1 (mNotch1-IC), mimicking in the presence of estrogen a constitutively active Notch receptor, was stably transfected into the Burkitt's lymphoma cell lines BL41-P3HR1 and HH514. Northern blot analysis revealed that the LMP2A gene is induced by Notch-IC in the presence of estrogen, whereas increased expression of LMP1 could be detected only if cycloheximide was simultaneously added. Concerning the cellular genes regulated by EBNA2, Notch-IC was able to upregulate CD21 but not CD23 expression. Immunoglobulin mu (Igmu) expression, which is downregulated by EBNA2, was also negatively regulated by Notch-IC. Similarly to EBNA2, Notch-IC was able to repress c-myc expression, which is under the control of the immunoglobulin heavy-chain locus in Burkitt's lymphoma cells with a t(8;14) translocation. The data show that Notch-IC is able to participate in gene regulation in B cells.
Strobl
L J
LJ
GSF-National Research Center for Environment and Health, Institute for Clinical Molecular Biology and Tumor Genetics, D-81377 Munich, Germany.
Höfelmayr
H
H
Marschall
G
G
Brielmeier
M
M
Bornkamm
G W
GW
Zimber-Strobl
U
U
D000818:Animals; D001402:B-Lymphocytes; D001665:Binding Sites; D002051:Burkitt Lymphoma; D002462:Cell Membrane / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics; D015536:Down-Regulation; D019309:Epstein-Barr Virus Nuclear Antigens / Q000378:metabolism*; D004967:Estrogens / Q000378:metabolism; D005786:Gene Expression Regulation; D004854:Herpesvirus 4, Human; D006801:Humans; D051819:Immunoglobulin J Recombination Signal Sequence-Binding Protein; D007148:Immunoglobulin mu-Chains / Q000235:genetics; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D009687:Nuclear Proteins; D011401:Promoter Regions, Genetic; D016271:Proto-Oncogene Proteins c-myc / Q000235:genetics; D051881:Receptor, Notch1; D011956:Receptors, Cell Surface; D017464:Receptors, Complement 3d / Q000235:genetics; D017455:Receptors, IgE / Q000235:genetics; D014157:Transcription Factors; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D014162:Transfection; D014407:Tumor Cells, Cultured; D015854:Up-Regulation; D014763:Viral Matrix Proteins / Q000235:genetics
D004268:DNA-Binding Proteins; C037662:EBV-associated membrane antigen, Epstein-Barr virus; D019309:Epstein-Barr Virus Nuclear Antigens; D004967:Estrogens; D051819:Immunoglobulin J Recombination Signal Sequence-Binding Protein; D007148:Immunoglobulin mu-Chains; D008565:Membrane Proteins; C497761:NOTCH1 protein, human; C497762:Notch1 protein, mouse; D009687:Nuclear Proteins; D016271:Proto-Oncogene Proteins c-myc; C497570:RBPJ protein, human; C497571:Rbpj protein, mouse; D051881:Receptor, Notch1; D011956:Receptors, Cell Surface; D017464:Receptors, Complement 3d; D017455:Receptors, IgE; D014157:Transcription Factors; D014763:Viral Matrix Proteins