Ectopic expression of myc or myn down-regulates immunoglobulin transcription.
Co-transfection of expression vectors for c-myc or myn down-regulated the expression from a reporter plasmid containing the chloramphenicol-acetyl-transferase (CAT) gene, under the control of an immunoglobulin kappa promoter and the immunoglobulin heavy-chain enhancer. The effect was dose-dependent and an additive effect was seen when both expression vectors were transfected simultaneously. Deletion mutants lacking the leucine zipper region of c-myc were unable to down-regulate the transcription from the reporter construct. Reporter genes where the immunoglobulin enhancer had been exchanged with a SV40 enhancer or an immunoglobulin minimal enhancer were still down-regulated by a cotransfection with c-myc expression vectors. A minimal promoter containing an octamer motif responded to myc expression while a minimal promoter containing a SP1 motif did not. No direct interactions between myc, myn and Oct proteins could be detected either by band-shift analysis, or by co-translation in vitro followed by precipitation with SP6 kappa promoter bound to magnetic carriers. Furthermore, B cells from mice transgenic for myc showed aberrant expression of transcription factors.
Immunology Unit, Lund University, Sweden.
M
M
Sigvardsson
K
K
Johansson
L G
LG
Larsson
K
K
Nilsson
T
T
Leanderson
D000818:Animals; D001402:B-Lymphocytes / Q000502:physiology; D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D004268:DNA-Binding Proteins / Q000235:genetics / Q000502:physiology*; D015536:Down-Regulation / Q000502:physiology*; D015870:Gene Expression; D005803:Genes, Immunoglobulin; D016259:Genes, myc; D007145:Immunoglobulin kappa-Chains / Q000502:physiology; D007136:Immunoglobulins / Q000096:biosynthesis / Q000235:genetics*; D051379:Mice; D008807:Mice, Inbred BALB C; D008822:Mice, Transgenic; D011401:Promoter Regions, Genetic / Q000502:physiology; D016271:Proto-Oncogene Proteins c-myc / Q000235:genetics / Q000502:physiology*; D014157:Transcription Factors / Q000502:physiology; D014158:Transcription, Genetic / Q000502:physiology*
D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D004268:DNA-Binding Proteins; D007145:Immunoglobulin kappa-Chains; D007136:Immunoglobulins; D016271:Proto-Oncogene Proteins c-myc; D014157:Transcription Factors; C068422:Max protein, mouse