Interaction of cell-type-specific nuclear proteins with immunoglobulin VH promoter region sequences

All human and murine immunoglobulin heavy chain variable region (V H ) genes contain the sequence ATGCAAAT approximately 70 nucleotides 5′ from the site of transcription initiation 1,2 . This octanucleotide, in reverse orientation, is also found in all light chain variable region (V L ) genes 1,2 , and in the immunoglobulin heavy chain transcriptional enhancer 2 . Transfection studies have established that this octamer is involved in the lyraphoid-specific transcription of immunoglobulin genes 2–6 . Octamer-containing fragments have been reported to bind a factor present in nuclear extracts of human cell lines; however, identical binding activity was detected in both B lymphoid and non-lymphoid cells 7 . Here we establish that nuclear extracts from distinct cell types differ in their ability to interact with octamer-containing fragments. We have also detected a DNA-protein interaction that may be involved in the cell-type specificity of immunoglobulin expression, and we have determined that a sequence upstream of the octamer participates in an interaction with a nuclear protein(s).