Pharmacology Division, National Cancer Center Research Institute, Tokyo, Japan.
Members of the ATP binding cassette (ABC) superfamily are involved in the energy-dependent transport of a wide variety of substrates including anticancer agents across the membranes. We have cloned a cDNA fragment including a novel ABC sequence from a cisplatin-resistant human lung adenocarcinoma cell line, PC-14/CDDP, by reverse transcription polymerase chain reaction (RT-PCR) using degenerate primers and screened a cDNA library using the cDNA fragment as a probe. A full-length cDNA clone, BM4.8, was obtained. Sequence analysis showed that the cDNA encoded a short type of multidrug resistance protein homologue, SMRP, by computed homology search. SMRP was composed of 946 amino acids and had two ABCs with walker A and B motifs. This gene was mapped on chromosome 3 at band q27 by fluorescence in situ hybridization (FISH) analysis and was found to be expressed in various tissues by Northern blot analysis.