The 4F2 heavy chain gene: a molecular model of inducible gene expression in human T cells.
We have utilized the human 4F2 heavy chain (4F2HC) gene as a model system in studies designed to elucidate the molecular events involved in regulating inducible gene expression during normal human T-cell activation. In previous studies we have shown that steady state levels of 4F2HC mRNA are induced 50-60-fold within 6 h of T-cell activation by phytohemagluttinin (PHA) and that the induction of 4F2HC gene expression involves both the protein kinase C and calcium-mediated activation pathways. Despite the fact that the 4F2HC gene is highly regulated in T cells, the 5' upstream region of the 4F2HC gene contains a housekeeping promoter which is G + C rich, lacks TATA or CCAAT sequences, and contains four potential binding sites for the ubiquitous Sp 1 transcription factor. The major regulatory elements of the 4F2HC gene do not reside within this 5' upstream region but instead, map to the exon 1-intron 1 region of the gene. The low levels of mature 4F2HC mRNA in resting T cells result from a block to transcription elongation within the exon 1-intron 1 region of the gene rather than promoter inactivity. Phorbol ester stimulation of resting T cells induces 4F2HC expression by removing this block to transcription elongation. We now report that in addition to its ability to serve as a transcriptional attenuator, the 4F2HC first intron contains a powerful enhancer element which is active in a wide variety of cell types including malignant human T cells. Full enhancer activity is displayed by a 186 bp fragment of the first intron which contains binding sites for two novel nuclear proteins (NF-4FA and NF-4FB) which flank a consensus binding site for the AP-1 transcription factor. A cDNA encoding the NF-4FB enhancer binding protein has been cloned by screening a lambda gt11 cDNA library with a rabiolabelled oligonucleotide corresponding to the NF-4FB recognition sequence.
Leiden
J M
JM
Howard Hughes Medical Institute, University of Michigan Medical Center, Ann Arbor 48109.
Yang
L H
LH
Morle
G D
GD
June
C H
CH
Lindsten
T
T
Thompson
C B
CB
Karpinski
B
B
D000954:Antigens, Surface / Q000235:genetics; D001483:Base Sequence; D001665:Binding Sites; D003001:Cloning, Molecular; D004247:DNA / Q000235:genetics; D004742:Enhancer Elements, Genetic; D027261:Fusion Regulatory Protein-1; D005786:Gene Expression Regulation; D005803:Genes, Immunoglobulin; D006801:Humans; D007438:Introns; D008213:Lymphocyte Activation; D008957:Models, Genetic; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000235:genetics; D015183:Restriction Mapping; D013601:T-Lymphocytes / Q000276:immunology*
D000954:Antigens, Surface; D027261:Fusion Regulatory Protein-1; D009687:Nuclear Proteins; D004247:DNA