title: Point mutations in the Moloney murine leukemia virus enhancer identify a lymphoid-specific viral core motif and 1,3-phorbol myristate acetate-inducible element.
abstract: The transcriptional enhancer of the Moloney murine leukemia virus (MoMLV) is organized as a 75-base-pair repeat, and in each copy of the repeat there are multiple binding sites for nuclear factors. We have introduced point mutations into each of the known nuclear factor-binding sites in the MoMLV enhancer, in both copies of the direct repeat, and have analyzed the transcriptional activity conferred by the mutated enhancers by transient-expression assays in both hematopoietic and nonhematopoietic cell lines. Mutation of individual binding sites in the MoMLV enhancer has moderate effects (less than 2-fold to 20-fold) on transcription in six independent cell lines. Several mutations decreased transcription from the MoMLV enhancer ubiquitously (the leukemia virus factor b site and the glucocorticoid response element), whereas others affected transcription specifically in lymphoid cell lines (core motif) or, more significantly, in fibroblasts (nuclear factor 1 site). The transcriptional activity of the MoMLV enhancer can be induced 8- to 10-fold by 1,3-phorbol myristate acetate in Jurkat T cells. Mutations in any of three adjacent binding sites (leukemia virus factor b and c sites and the core motif) within a 28-base-pair region in the center of the direct repeat sequence of the MoMLV enhancer completely attenuate the response to 1,3-phorbol myristate acetate.
authors.affiliation: Center for Cancer Research, Massachusetts Institute of Technology, Cambridge 02139.
authors.forename: N A
authors.initials: NA
authors.lastname: Speck
authors.forename: B
authors.initials: B
authors.lastname: Renjifo
authors.forename: N
authors.initials: N
authors.lastname: Hopkins
mesh_terms: D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D004279:DNA, Viral / Q000187:drug effects / Q000235:genetics*; D004742:Enhancer Elements, Genetic / Q000187:drug effects*; D005814:Genes, Viral / Q000187:drug effects; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D008979:Moloney murine leukemia virus / Q000235:genetics*; D009154:Mutation; D010957:Plasmids; D011401:Promoter Regions, Genetic / Q000187:drug effects; D011505:Protein-Tyrosine Kinases / Q000235:genetics; D011518:Proto-Oncogene Proteins / Q000235:genetics; D016760:Proto-Oncogene Proteins c-fos; D011519:Proto-Oncogenes / Q000187:drug effects; D051381:Rats; D012091:Repetitive Sequences, Nucleic Acid; D015183:Restriction Mapping; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D014158:Transcription, Genetic / Q000187:drug effects
chemical_list: D004279:DNA, Viral; D011518:Proto-Oncogene Proteins; D016760:Proto-Oncogene Proteins c-fos; D011505:Protein-Tyrosine Kinases; D013755:Tetradecanoylphorbol Acetate