A somatic knockout of CBF1 in a human B-cell line reveals that induction of CD21 and CCR7 by EBNA-2 is strictly CBF1 dependent and that downregulation of immunoglobulin M is partially CBF1 independent.
CBF1 is a cellular highly conserved DNA binding factor that is ubiquitously expressed in all tissues and acts as a repressor of cellular genes. In Epstein-Barr virus growth-transformed B-cell lines, CBF1 serves as a central DNA adaptor molecule for several viral proteins, including the viral transactivator Epstein-Barr virus nuclear antigen 2 (EBNA-2). EBNA-2 binds to CBF1 and thereby gains access to regulatory regions of target genes and activates transcription. We have inactivated the CBF1 gene by homologous recombination in the human B-cell line DG75 and characterized changes in cellular gene expression patterns upon loss of CBF1 and activation of EBNA-2. CBF1-negative DG75 cells were viable and proliferated at wild-type rates. Loss of CBF1 was not sufficient to release repression of the previously described EBNA-2 target genes CD21 or CCR7, whereas induction of both target genes by EBNA-2 required CBF1. In contrast, repression of immunoglobulin M by EBNA-2 was mainly CBF1 independent. CBF1-negative DG75 B cells thus provide an excellent tool to dissect CBF1-dependent and -independent functions exerted by the EBNA-2 protein in future studies.
Maier
Sabine
S
Institute of Clinical Molecular Biology, GSF National Research Center for Environment and Health, Marchioninistr. 25, D-81377 Munich, Germany.
Santak
Maja
M
Mantik
Anja
A
Grabusic
Kristina
K
Kremmer
Elisabeth
E
Hammerschmidt
Wolfgang
W
Kempkes
Bettina
B
D000483:Alleles; D002051:Burkitt Lymphoma / Q000276:immunology*; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000235:genetics / Q000502:physiology*; D019309:Epstein-Barr Virus Nuclear Antigens / Q000502:physiology*; D006801:Humans; D051819:Immunoglobulin J Recombination Signal Sequence-Binding Protein; D007075:Immunoglobulin M / Q000096:biosynthesis*; D009687:Nuclear Proteins / Q000235:genetics / Q000502:physiology*; D016271:Proto-Oncogene Proteins c-myc / Q000096:biosynthesis; D054400:Receptors, CCR7; D019707:Receptors, Chemokine / Q000096:biosynthesis*; D017464:Receptors, Complement 3d / Q000096:biosynthesis*; D014764:Viral Proteins
C515370:CCR7 protein, human; D004268:DNA-Binding Proteins; C402641:EBNA-2 protein, Human herpesvirus 4; D019309:Epstein-Barr Virus Nuclear Antigens; D051819:Immunoglobulin J Recombination Signal Sequence-Binding Protein; D007075:Immunoglobulin M; D009687:Nuclear Proteins; D016271:Proto-Oncogene Proteins c-myc; C497570:RBPJ protein, human; D054400:Receptors, CCR7; D019707:Receptors, Chemokine; D017464:Receptors, Complement 3d; D014764:Viral Proteins