The human multidrug resistance (mdr1) gene. cDNA cloning and transcription initiation - PubMed (original) (raw)

. 1987 Jan 15;262(2):505-8.

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The human multidrug resistance (mdr1) gene. cDNA cloning and transcription initiation

K Ueda et al. J Biol Chem. 1987.

Free article

Abstract

Multidrug resistance in human KB carcinoma cells selected for resistance to colchicine, vinblastine, or adriamycin results from overexpression, and frequently amplification, of a specific gene (mdr1). Overlapping cDNA clones representing a complete 4.7-kilobase mdr1 transcript have been obtained from multidrug-resistant KB cells. Primer extension and S1 nuclease protection experiments show that two transcripts initiate 136 and 140 bases upstream from the first ATG codon in all human multidrug-resistant cell lines. The mdr1 gene is expressed in human normal kidney cells and HepG2 liver cells as a poly(A)+ RNA which starts from the same sites. Less prominent transcripts were found to initiate 155-180 bases upstream from the first ATG codon in vinblastine- or adriamycin-selected cell lines and 480-630 bases upstream in colchicine-selected cell lines. Southern hybridization analyses with different portions of a full-length cDNA indicate that the human mdr1 gene encompasses at least 70 kilobases of DNA amplified in all highly multidrug-resistant cell lines.

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