NF-kappa B activity is required for the deregulation of c-myc expression by the immunoglobulin heavy chain enhancer.
The c-myc gene is translocated to one of the immunoglobulin genes in Burkitt's lymphoma resulting in deregulated expression of c-myc. Several enhancers have been shown to be important for expression of the immunoglobulin heavy chain gene. Four enhancer regions (murine-hypersensitive sites (MHS) 1, 2, 3, and 4) located 3' of the murine immunoglobulin heavy chain gene play a role in activating expression of the translocated c-myc gene. The enhancer regions also result in a shift in transcriptional initiation from the P2 promoter to P1 that is characteristic of the translocated c-myc allele. We found that the most 3' enhancer region (MHS4) activated the c-myc promoter by 46-fold in the Raji Burkitt's lymphoma cell line, and it was the most active enhancer in these cells. The addition of enhancer regions MHS1,2 and 3 to MHS4 increased c-myc transcription by an additional 3-fold and resulted in the full promoter shift from P2 to P1. By deletion analysis of enhancer region MHS4, we located a region that was critical for the transcriptional activity of MHS4. Electrophoretic mobility shift assay analysis revealed that NF-kappaB/Rel family members bound to this region. Mutation of the NF-kappaB binding site abolished both the enhancer activity and the promoter shift activity of MHS4. An active NF-kappaB site was also identified in the human HS4 enhancer. Inhibition of c-myc promoter activity driven by the immunoglobulin enhancers was observed with expression of a super-repressor IkappaBalpha construct. These results indicate that the NF-kappaB/Rel transcription factors play an important role in the deregulation of the translocated c-myc gene in Burkitt's lymphoma and suggest that interference with NF-kappaB function may represent a new approach to the treatment of Burkitt's lymphoma.
Kanda
K
K
Center for Molecular Biology in Medicine, Veterans Affairs Palo Alto Health Care System and the Department of Medicine, Stanford University School of Medicine, Stanford, California 94305, USA.
Hu
H M
HM
Zhang
L
L
Grandchamps
J
J
Boxer
L M
LM
D000818:Animals; D001483:Base Sequence; D002051:Burkitt Lymphoma / Q000235:genetics*; D004247:DNA / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D004742:Enhancer Elements, Genetic / Q000235:genetics*; D015972:Gene Expression Regulation, Neoplastic; D016259:Genes, myc / Q000235:genetics*; D006801:Humans; D020672:I-kappa B Proteins; D007143:Immunoglobulin Heavy Chains / Q000235:genetics*; D051379:Mice; D009154:Mutation / Q000235:genetics; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism*; D052002:NF-kappa B p50 Subunit; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D012333:RNA, Messenger / Q000032:analysis / Q000235:genetics; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism; D020218:Response Elements / Q000235:genetics; D051996:Transcription Factor RelA; D014162:Transfection; D014178:Translocation, Genetic / Q000235:genetics; D014407:Tumor Cells, Cultured
D004268:DNA-Binding Proteins; D020672:I-kappa B Proteins; D007143:Immunoglobulin Heavy Chains; D016328:NF-kappa B; D052002:NF-kappa B p50 Subunit; C000606204:NFKBIA protein, human; C000606205:Nfkbia protein, mouse; D012333:RNA, Messenger; D012097:Repressor Proteins; D051996:Transcription Factor RelA; D000072000:NF-KappaB Inhibitor alpha; D004247:DNA