title: The c-myc protein represses the lambda 5 and TdT initiators.
abstract: The lambda 5 promoter initiates transcription at multiple sites and confers expression in all cell types. Two lambda 5 promoter-derived oligonucleotides (Inr lambda 5:1 and Inr lambda 5:2), each with a transcription start site, could promote transcription in transient transfection assays. In contrast, a third oligonucleotide (+90 lambda 5), without a transcription initiation site, was inactive. The Inr lambda 5:1 and Inr lambda 5:2 oligonucleotides formed a major DNA-protein complex B' in gel retardation analyses; no protein-DNA complexes were observed with the inactive +90 lambda 5 oligonucleotide. The B' complexes of Inr lambda 5:1 and Inr lambda 5:2 each contained c-myc and myn (murine homologue of Max) proteins. The c-myc and myn proteins were also found to bind the TdT initiator (InrTdT). Using mutated oligonucleotides, we found that the c-myc/myn proteins bound to the transcription initiation site of both Inr lambda 5:1 and InrTdT, however, these mutated oligonucleotides were inactive in transfection assays. This suggested that, in this system, transcription depended both on a transcription initiation site and appropriate flanking sequences. The significance of c-myc binding to the respective initiator was analysed by overexpressing c-myc in co-transfection assays. Under these conditions the transcriptional activity of both the lambda 5 and the TdT initiator was repressed.
authors.affiliation: Basel Institute for Immunology, Switzerland.
authors.forename: S
authors.initials: S
authors.lastname: Mai
authors.forename: I L
authors.initials: IL
authors.lastname: Mårtensson
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001402:B-Lymphocytes / Q000378:metabolism; D001483:Base Sequence; D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D001665:Binding Sites / Q000235:genetics; D002460:Cell Line; D004247:DNA / Q000235:genetics / Q000378:metabolism; D004253:DNA Nucleotidylexotransferase / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D015536:Down-Regulation; D005822:Genetic Vectors; D051379:Mice; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D016271:Proto-Oncogene Proteins c-myc / Q000235:genetics / Q000378:metabolism*; D016601:RNA-Binding Proteins; D012097:Repressor Proteins / Q000378:metabolism*; D012269:Ribosomal Proteins / Q000235:genetics*; D014158:Transcription, Genetic; D014162:Transfection
chemical_list: D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D004268:DNA-Binding Proteins; D016271:Proto-Oncogene Proteins c-myc; D016601:RNA-Binding Proteins; D012097:Repressor Proteins; D012269:Ribosomal Proteins; C084343:Rpl29 protein, mouse; C068422:Max protein, mouse; D004247:DNA; D004253:DNA Nucleotidylexotransferase