Structure of the 5' ends of immunoglobulin genes: a novel conserved sequence.

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Abstract
Apparently, tissue-specific regulatory factors are required for Ig gene transcription. Cells of the mouse lymphocytoid pre-B-cell line 70Z/3 contain a constitutively rearranged Ig .kappa. L chain gene; the nucleotide sequence of this gene exhibits all the known properties of a functionally competent transcription unit. Nevertheless, transcripts derived from this gene are detectable only after exposure of the cells to bacterial lipopolysaccharide, implying that accurate DNA rearrangement is not sufficient to activate expression of the gene. Comparison of the sequence of the 70Z/3 .kappa. L chain gene with those encoding other Ig H and L chains has revealed that a distinctive promoter region structure is characteristic of this multigene family. The sequence A-T-T-T-G-C-A-T lies .apprx. 70 base pairs upstream from the site of transcriptional initiation in every L chain gene examined; in H chain genes, the corresponding location is occupied by the precise inverse (A-T-G-C-A-A-A-T) of this sequence. Although adjacent regions of DNA have diverged extensively in evolution, these octanucleotide seqeunces are stringently conserved at this location among diverse Ig genes from at least 2 mammalian species. The proximity of this conserved octanucleotide block to the site of transcriptional initiation suggests that it may serve as a recognition locus for factors regulating Ig gene expression in a tissue-specific fashion.