Importance of the Two Interferon-stimulated Response Element (ISRE) Sequences in the Regulation of the Human Indoleamine 2,3-Dioxygenase Gene

Indoleamine 2,3-dioxygenase (INDO) is the rate-limiting enzyme in the catabolism of the essential amino acid L -tryptophan. It is induced strongly in many cell lines following interferon-γ treatment. We report the cloning and characterization of the full-length human INDO promoter. This promoter is...

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Bibliographic Details
Published in:The Journal of biological chemistry 1996-08, Vol.271 (32), p.19140-19145
Main Authors: Konan, K V, Taylor, M W
Format: Article
Language:English
Subjects:
Base Sequence
Chloramphenicol O-Acetyltransferase - genetics
Cloning, Molecular
DNA, Complementary
Gene Expression Regulation, Enzymologic - genetics
Humans
Interferon-gamma - pharmacology
Molecular Sequence Data
Mutagenesis, Site-Directed
Promoter Regions, Genetic
Sequence Deletion
Tryptophan Oxygenase - genetics
Tumor Cells, Cultured
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Summary:Indoleamine 2,3-dioxygenase (INDO) is the rate-limiting enzyme in the catabolism of the essential amino acid L -tryptophan. It is induced strongly in many cell lines following interferon-γ treatment. We report the cloning and characterization of the full-length human INDO promoter. This promoter is 1,245 base pairs long and includes two interferon-stimulated response elements (ISRE) separated by an approximately 1-kilobase sequence. The presence of these two ISREs is critical for maximum INDO promoter activity (50-fold induction). When the ISREs are present in two separate fragments cloned upstream of the chloramphenicol acetyltransferase (CAT) reporter vector, the INDO promoter activity drops significantly (7-fold induction). 5′ end deletions of the wild type promoter sequence indicate that removal of the ISRE (ISRE1) at position −1126 reduces the induction level to approximately 25-fold. This activity does not change appreciably when the promoter is deleted down to position −241. Furthermore, site-directed mutagenesis of ISRE1 also decreases the promoter activity in a similar way. When ISRE1 is kept intact, deletion of the second ISRE (ISRE2) at position −111 leads to only 11-fold induction of the promoter. A similar result is obtained when substitution mutations are introduced in ISRE2. Deletion of a 748-base pair sequence between the two ISREs only shows a slight decrease in the INDO promoter activity. These data indicate that the two ISRE sequences are required for the full transcriptional induction of the interferon-γ-inducible human INDO gene. INDO activity is not induced in the hepatic cell line HepG2. An analysis of INDO-CAT activity in this cell line indicated that the lack of INDO activity was at the transcriptional level and could reflect either the presence of a repressor or lack of a transcription factor. This lack of induction could be correlated with a truncated or unstable IRF-1. However, the levels of IRF-2, JAK2, and STAT 91 were similar in both ME180 and HepG2 cells.
ISSN:0021-9258
1083-351X
DOI:10.1074/jbc.271.32.19140