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

All human and murine immunoglobulin heavy chain variable region (VH) genes contain the sequence ATGCAAAT approximately 70 nucleotides 5' from the site of transcription initiation. This octanucleotide, in reverse orientation, is also found in all light chain variable region (VL) genes, and in the immunoglobulin heavy chain transcriptional enhancer. Transfection studies have established that this octamer is involved in the lymphoid-specific transcription of immunoglobulin genes. 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. 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).