The ubiquitous octamer-binding protein(s) is sufficient for transcription of immunoglobulin genes.
All immunoglobulin genes contain a conserved octanucleotide promoter element, ATGCAAAT, which has been shown to be required for their normal B-cell-specific transcription. Proteins that bind this octamer have been purified, and cDNAs encoding octamer-binding proteins have been cloned. Some of these proteins (referred to as OTF-2) are lymphoid specific, whereas at least one other, and possibly more (referred to as OTF-1), is found ubiquitously in all cell types. The exact role of these different proteins in directing the tissue-specific expression of immunoglobulin genes is unclear. We have identified two human pre-B-cell lines that contain extremely low levels of OTF-2 yet still express high levels of steady-state immunoglobulin heavy-chain mRNA in vivo and efficiently transcribe an immunoglobulin gene in vitro. Addition of a highly enriched preparation of OTF-1 made from one of these pre-B cells or from HeLa cells specifically stimulated in vitro transcription of an immunoglobulin gene. Furthermore, OFT-1 appeared to have approximately the same transactivation ability as OTF-2 when normalized for binding activity. These results suggest that OTF-1, without OTF-2, is sufficient for transcription of immunoglobulin genes and that OTF-2 alone is not responsible for the B-cell-specific regulation of immunoglobulin gene expression.
Johnson
D G
DG
Department of Microbiology, Southwestern Medical Center, Dallas, Texas 75235-9096.
Carayannopoulos
L
L
Capra
J D
JD
Tucker
P W
PW
Hanke
J H
JH
D001483:Base Sequence; D015152:Blotting, Northern; D002467:Cell Nucleus / Q000502:physiology; D004268:DNA-Binding Proteins / Q000502:physiology*; D005786:Gene Expression Regulation; D005803:Genes, Immunoglobulin; D006801:Humans; D066298:In Vitro Techniques; D008214:Lymphocytes / Q000502:physiology*; D008969:Molecular Sequence Data; D015345:Oligonucleotide Probes; D011401:Promoter Regions, Genetic; D015183:Restriction Mapping; D014157:Transcription Factors / Q000502:physiology; D014158:Transcription, Genetic; D014407:Tumor Cells, Cultured
D004268:DNA-Binding Proteins; D015345:Oligonucleotide Probes; D014157:Transcription Factors