Tissue-specific enhancer of the human multidrug-resistance (MDR1) gene

K. Kohno, S. Sato, T. Uchiumi, H. Takano, S. Kato, M. Kuwano

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58 Citations (Scopus)

Abstract

Identification of cis-regulatory sequences is a first step in analyzing the regulation of the human multidrug-resistant 1 (MDR1) gene which encodes the 170-kilodalton membrane P-glycoprotein in normal tissues and tumor cells. We have studied several overlapping genomic clones containing the 5'-flanking region of the gene. These clones span about 30 kilobases (kb) of contiguous DNA containing 10 kb of the gene and 20 kb of the 5'-flanking sequence. The nucleotide sequence of the first exon and the 2 kb preceding the exon were determined. DNA sequences containing the 5'-flanking regions were linked to the chloramphenicol acetyltransferase (CAT) gene. For transient CAT assay, we have employed six cell lines, including human cancer KB, vincristine-resistant VJ-300 derived from KB, mouse adrenal tumor Y-1, African green monkey kidney CV-1, mouse fibroblast NIH3T3, and human adrenal carcinoma SW-13 cells. Promoter activity was very weak regardless of the length of the promoter region in mouse adrenal tumor Y-1 and monkey kidney CV-1 cells, in which endogenous P-glycoprotein was expressed. Introduction of a 700-base genomic DNA fragment from a site located at 10 kb far upstream of the initiation site increased the transcription of the CAT gene in Y-1, CV-1, and SW-13 cells. However, no significant increase in the CAT activity could be observed in NIH3T3, KB, and VJ-300 cells. This fragment markedly augmented the expression of the CAT gene regardless of orientation or position, and it acted in a cell type-specific manner even with heterogeneous promoters. Our present study suggests that the 700-base pair fragment may carry a tissue-specific transcriptional enhancer that is active in at least some adrenal and kidney-derived cell lines.

Original languageEnglish
Pages (from-to)19690-19696
Number of pages7
JournalJournal of Biological Chemistry
Volume265
Issue number32
Publication statusPublished - 1990
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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