A transcriptional enhancer element has been identified 4.5 kilobases 3' of C. (

We utilized the human 4F2 heavy-chain (4F2HC) gene as a model system to study the regulation of inducible gene expression during normal human T-cell activation. Previous studies have demonstrated that 4F2HC gene expression is induced during normal T-cell activation and that the activity of the gene is regulated, at least in part, by the interaction of a constitutively active 5'-flanking housekeeping promoter and a phorbol ester-responsive transcriptional attenuator element located in the exon 1-intron I region of the gene. We now report that 4F2HC intron 1 contains a transcriptional enhancer element which is active on a number of heterologous promoters in a variety of murine and human cells. This enhancer element has been mapped to a 187-base-pair RsaI-AluI fragment from 4F2HC intron 1. DNase I footprinting and gel mobility shift analyses demonstrated that this fragment contains two nuclear protein-binding sites (NF-4FA and NF-4FB) which flank a consensus binding site for the inducible AP-I transcription factor. Deletion analysis showed that the NF-4FA, NF-4FB, and AP-1 sequences are each necessary for full enhancer activity. Murine 4F2HC intron I displayed enhancer activity similar to that of its human counterpart. Comparison of the sequences of human and murine 4F2HC intron ls demonstrated that the NF-4FA, NF-4FB, and AP-1 sequence motifs have been highly conserved during mammalian evolution.Antigen recognition by the heterodimeric a-13 receptor of human T lymphocytes (TCR a-1) results in a complex and precisely orchestrated set of changes in T-cell gene expression, including induction of a set of nuclear proto-oncogenes (19,33), production of a variety of soluble lymphokines (34), and expression of a novel group of cell surface antigens (9). While a great deal has recently been learned about the structural requirements for antigen recognition by the TCR (x-I molecule (for a review, see reference 11), less is understood about the molecular mechanisms involved in modulating inducible gene expression during T-cell activation. Cross-linking of the TCR ot-r-CD3 complex has been shown to result in phosphoinositol turnover, protein kinase C activation, and transient increases in cytosolic ionized calcium levels (for a review, see reference 1). How these and other second messengers subsequently regulate T-cell gene expression remains unclear.We have utilized the 4F2 cell-surface antigen as a model system of gene regulation during human T-cell activation. 4F2 is a 120-kilodalton disulfide-linked heterodimer composed of an 85-kilodalton glycosylated heavy chain (4F2HC) and a 35-kilodalton nonglycosylated light chain (4F2LC) (18). 4F2 is of interest in studies of T-cell activation because it is a T-cell activation antigen which is expressed at low levels on resting peripheral blood T cells and is rapidly induced after activation with lectins or antigen (9). Increases in cell surface expression of 4F2 first occur 4 h after lectin stimulation and peak at 16 to 20 h, before the onset of DNA synthesis or the appearance of t...

We utilized the human 4F2 heavy-chain (4F2HC) gene as a model system to study the regulation of inducible gene expression during normal human T-cell activation. Previous studies have demonstrated that 4F2HC gene expression is induced during normal T-cell activation and that the activity of the gene is regulated, at least in part, by the interaction of a constitutively active 5'-flanking housekeeping promoter and a phorbol ester-responsive transcriptional attenuator element located in the exon 1-intron 1 region of the gene. We now report that 4F2HC intron 1 contains a transcriptional enhancer element which is active on a number of heterologous promoters in a variety of murine and human cells. This enhancer element has been mapped to a 187-base-pair RsaI-AluI fragment from 4F2HC intron 1. DNase I footprinting and gel mobility shift analyses demonstrated that this fragment contains two nuclear protein-binding sites (NF-4FA and NF-4FB) which flank a consensus binding site for the inducible AP-1 transcription factor. Deletion analysis showed that the NF-4FA, NF-4FB, and AP-1 sequences are each necessary for full enhancer activity. Murine 4F2HC intron 1 displayed enhancer activity similar to that of its human counterpart. Comparison of the sequences of human and murine 4F2HC intron 1s demonstrated that the NF-4FA, NF-4FB, and AP-1 sequence motifs have been highly conserved during mammalian evolution.