Octamer transcription factors and the cell type-specificity of immunoglobulin gene expression.
Antibodies are produced exclusively in B lymphocytes. The expression of the antibody-encoding genes, the immunoglobulin (Ig) genes, is also restricted to B cells. The octamer sequence ATGCAAAT is present in the promoter and the enhancer of Ig genes, and plays an important role in its tissue-specific expression. This sequence motif is a binding site for nuclear proteins, the so-called octamer transcription factors (Oct or OTF factors). The Oct-1 protein is present in all cell types analyzed so far, whereas Oct-2A and Oct-2B are found mainly in B lymphocytes. All three proteins show the same sequence specificity and binding affinity. It appears that the B cell-specific expression of Ig genes is mediated at least in part by cell type-specific Oct factors, and that there are both quantitative and qualitative differences between Oct-1 and Oct-2 factors. Recently, a number of other octamer factor variants were identified. Many of these may be created by alternative splicing of a primary transcript of one Oct factor gene and may serve a specific function in the fine tuning of gene expression.
Kemler
I
I
Institut für Molekularbiologie II, Universität Zürch, Switzerland.
Schaffner
W
W
D000595:Amino Acid Sequence; D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology; D001483:Base Sequence; D004268:DNA-Binding Proteins / Q000235:genetics; D005786:Gene Expression Regulation / Q000276:immunology*; D005803:Genes, Immunoglobulin / Q000235:genetics*; D051863:Host Cell Factor C1; D006801:Humans; D008969:Molecular Sequence Data; D050811:Octamer Transcription Factor-1; D050813:Octamer Transcription Factor-2; D012326:RNA Splicing / Q000235:genetics; D014157:Transcription Factors / Q000235:genetics*
D004268:DNA-Binding Proteins; C497692:HCFC1 protein, human; D051863:Host Cell Factor C1; C059328:Oct-2B protein, mouse; D050811:Octamer Transcription Factor-1; D050813:Octamer Transcription Factor-2; C494165:POU2F1 protein, human; C058435:POU2F2 protein, human; D014157:Transcription Factors