title: Protein-nucleotide contacts in the immunoglobulin heavy-chain promoter region.
abstract: Immunoglobulin heavy-chain variable-region genes contain the octanucleotide ATGCAAAT upstream from the site of transcription initiation. The complement of this sequence, in the reverse orientation, is found at an identical location in light-chain variable-region genes. This sequence element is thought to be involved in the lymphoid-specific expression of immunoglobulin genes. Analysis of nuclear extracts from both lymphoid and nonlymphoid cells in a gel migration inhibition assay, using an immunoglobulin promoter region fragment containing the octamer, reveals multiple migration-retarded species that represent specific DNA-protein complexes. The number and relative level of these complexes vary with cell type; some complexes are detected with all extracts, whereas one complex is lymphoid-specific and may represent an interaction involved in the lymphoid-restricted expression of immunoglobulin genes. Mitogenic stimulation of a B-lymphoid line can increase the level of the protein responsible for this lymphoid-specific complex. Analysis of the complexes detected in the gel migration inhibition assay by DNase I protection ("footprinting") has revealed that all of these DNA-protein complexes involve contact of the protein with the nucleotides of the octamer. One complex, present in both lymphoid and nonlymphoid cells, displays an additional DNA-protein contact adjacent to the octamer. Our results also indicate that the interaction of proteins with the octameric sequence can cause a local alteration in the structure of the DNA helix.
mesh_terms: D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology; D001483:Base Sequence; D003850:Deoxyribonuclease I; D005796:Genes; D007143:Immunoglobulin Heavy Chains / Q000235:genetics*; D007942:Leukemia, Experimental / Q000276:immunology; D008213:Lymphocyte Activation; D051379:Mice; D009690:Nucleic Acid Conformation; D011401:Promoter Regions, Genetic; D014158:Transcription, Genetic
chemical_list: D007143:Immunoglobulin Heavy Chains; D003850:Deoxyribonuclease I