Positive and negative regulation of the human insulin gene by multiple trans-acting factors.
Tissue-specific expression of the human insulin gene is regulated by cis-acting DNA elements 5' to the transcription start site. Deletion of the 5' region of the human insulin gene between nucleotides -279 and -258 caused a 25-fold rise in transcriptional activity whereas further deletion to nucleotide -229 reduced transcription activity 25-fold. In vitro analysis of protein binding in the 5' regulatory region revealed: (i) the major positive regulatory region (-258 to -229) contains a protein-binding site (GC-II) with 75% sequence identity to a motif in the rat insulin I gene, shown to be a powerful transcriptional activator. GC-II motif-binding factors are not restricted to insulin-producing cell lines. (ii) An islet cell-specific factor binds between nucleotides -217 to -210 (CT-II motif). (iii) A region between nucleotides -153 and -127, containing two identical motifs, GG-I and GG-II was also revealed. GG-I-binding factors are ubiquitous, whereas binding to the GG-II motif is beta cell-specific. (iv) A ubiquitous factor binds to a motif between nucleotides -179 and -183, identical to a half-site for the cyclic nucleotide regulatory element. (v) The negative regulatory element between -279 and -258 contains overlapping binding sites for at least 3 protein factors, with differing cell-specific distributions and can independently down-regulate thymidine kinase promoter activity in a beta cell line.
Department of Medicine, University of Birmingham, Queen Elizabeth Hospital, Edgbaston, United Kingdom.
D S
DS
Boam
A R
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Clark
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Docherty
D001483:Base Sequence; D001665:Binding Sites; D015500:Chloramphenicol O-Acetyltransferase / Q000235:genetics; D015536:Down-Regulation; D005786:Gene Expression Regulation; D006801:Humans; D007328:Insulin / Q000235:genetics*; D007515:Islets of Langerhans / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D012045:Regulatory Sequences, Nucleic Acid; D015183:Restriction Mapping; D015534:Trans-Activators / Q000502:physiology*; D014158:Transcription, Genetic; D014162:Transfection; D014407:Tumor Cells, Cultured
D007328:Insulin; D015534:Trans-Activators; D015500:Chloramphenicol O-Acetyltransferase