TFII-I regulates Vbeta promoter activity through an initiator element.
In our effort to understand the transcriptional regulation of naturally occurring TATA-less but initiator (Inr)-containing genes, we have employed the murine T-cell receptor Vbeta 5.2 promoter as a model. Here we show by transient-transfection assays that the Inr binding transcription factor TFII-I is required for efficient expression of the Vbeta promoter in vivo. Mutations in the Inr element that reduced binding of TFII-I also abolished the Vbeta promoter activity by ectopic TFII-I. We further biochemically identified a protease-resistant N-terminal DNA binding fragment of TFII-I, p70. When ectopically expressed, recombinant p70 bound to the Vbeta Inr element with a specificity similar to that of wild-type TFII-I. More importantly, p70, which lacks independent activation functions, behaved as a dominant negative mutant that inhibited Inr-specific function of wild-type TFII-I. However, the activation functions of p70 were restored when fused to the heterologous activation domain of the yeast activator protein GAL4. Taken together, these data suggest that TFII-I functions in vivo require an intact Inr element and that the Inr-specific transcriptional functions of TFII-I are solely dictated by its N-terminal DNA binding domain and do not require its own C-terminal activation domain.
Cheriyath
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Department of Pathology and Program in Immunology, Tufts University School of Medicine, Boston, Massachusetts 02111, USA.
Novina
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Roy
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D000818:Animals; D001419:Bacteria / Q000378:metabolism; D001665:Binding Sites; D019556:COS Cells; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D005786:Gene Expression Regulation; D051379:Mice; D011401:Promoter Regions, Genetic; D016693:Receptors, Antigen, T-Cell, alpha-beta / Q000235:genetics*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D013917:Thrombin / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic
D004268:DNA-Binding Proteins; D016693:Receptors, Antigen, T-Cell, alpha-beta; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; D004247:DNA; D013917:Thrombin