ABSTRACT

Inosine-5`-monophosphate dehydrogenase (IMPDH) activity and mRNA levels are induced up to 15-fold upon mitogenic or antigenic stimulation of human peripheral blood T lymphocytes. This increase in IMPDH activity is required for cellular proliferation and has been associated with malignant transformation. We have cloned the human IMPDH type II gene and show that it contains 14 exons and is approximately 5.8 kilobases in length. Exons vary in size from 49 to 207 base pairs and introns from 73 to 1065 base pairs. The transcription start site was mapped to a position 50 nucleotides upstream of the translation initiation site. The 5`-flanking region consisting of 463 base pairs upstream of the translation initiation site confers induced transcription and differential regulation upon a chloramphenicol acetyltransferase reporter gene when transfected into Jurkat T cells and human peripheral blood T lymphocytes, respectively. DNase I footprinting analysis using Jurkat T cell nuclear extract identified four protected regions in the promoter which coincide with consensus transcription factor binding sites for the nuclear factors AP2, ATF, CREB, Egr-1, Nm23, and Sp1. These findings suggest that several of these nuclear factors may play a critical role in the regulation of IMPDH type II gene expression during T lymphocyte activation.

FOOTNOTES

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This work was supported by National Institutes of Health Grants CA64192 and CA34085. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore by hereby marked ``advertisement'' in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

The nucleotide sequence(s) reported in this paper has been submitted to the GenBank(TM)/EMBL Data Bank with accession number(s) L39210[GenBank].

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To whom correspondence should be addressed: 1106 FLOB CB#7365, University of North Carolina, Chapel Hill, NC 27599-7365. Tel.: 919-966-4330; Fax: 919-966-5640.

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The abbreviations used are: IMPDH, inosine-5`-monophosphate dehydrogenase; bp, base pair(s); CAT, chloramphenicol acetyltransferase; DTT, dithiothreitol; kb, kilobase(s); PBS, phosphate-buffered saline; PMA, phorbol 12-myristate 13-acetate; PMSF, phenylmethylsulfonyl fluoride.

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