The helix-loop-helix containing transcription factor USF activates the promoter of the CD2 gene.
T cell development within the thymus involves the ordered expression of a number of tissue-specific components such as the CD2 gene. Control of expression of this gene is regulated by a well characterized 3' enhancer together with a promoter and upstream elements. The CD2 promoter is typical of a group of T cell-specific promoters that lack a TATA box and use multiple sites for initiation of transcription. An "E box" motif CACGTG, located just upstream from the most 5' initiation start site, was found to contribute a major effect to the level of basal transcription of a reporter gene. Analysis of the proteins in T cell extracts that bound to this site revealed that the bHLH-LZ protein USF was the major component. A functional role for USF was established in transient transfection experiments. Thus, this protein restored full promoter activity following repression caused by cotransfection with the E box binding bHLH-LZ protein Max. Taken together, these results indicate that an E box motif is critical to expression of the CD2 gene during T cell development and that the HLH protein USF acts as a transcriptional activator of the CD2 promoter.
Outram
S V
SV
Imperial Cancer Research Fund, London, United Kingdom.
Owen
M J
MJ
D001483:Base Sequence; D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D050976:Basic-Leucine Zipper Transcription Factors; D018801:CD2 Antigens / Q000235:genetics*; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000378:metabolism; D018257:Helix-Loop-Helix Motifs; D006801:Humans; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D014157:Transcription Factors / Q000502:physiology*; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D051720:Upstream Stimulatory Factors
D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D050976:Basic-Leucine Zipper Transcription Factors; D018801:CD2 Antigens; D004268:DNA-Binding Proteins; C499330:MAX protein, human; C067850:Myc associated factor X; D014157:Transcription Factors; C497181:USF1 protein, human; D051720:Upstream Stimulatory Factors