Sequence of Crm1/exportin 1 mutant alleles reveals critical sites associated with multidrug resistance (original) (raw)
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Molecular and General Genetics, 1994
TheSaccharomyces cerevisiae PDR3 gene, located near the centromere of chromosome II, has been completely sequenced and characterised. Mutationspdr3-1 andpdr3-2, which confer resistance to several antibiotics can be complemented by a wild-type allele of the PDR3 gene. The sequence of the wild-typePDR3 gene revealed the presence of a long open reading frame capable of encoding a 976-amino acid protein. The protein contains a single Zn(II)2Cys6 binuclear-type zinc finger homologous to the DNA-binding motifs of other transcriptional activators from lower eukaryotes. Evidence that the PDR3 protein is a transcriptional activator was provided by demonstrating that DNA-bound LexA-PDR3 fusion proteins stimulate expression of a nearby promoter containing LexA binding sites. The use of LexA-PDR3 fusions revealed that the protein contains two activation domains, one localised near the N-terminal, cysteine-rich domain and the other localised at the C-terminus. The salient feature of the PDR3 protein is its similarity to the protein coded byPDR1, a gene responsible forpleiotropicdrugresistance. The two proteins show 36% amino acid identity over their entire length and their zinc finger DNA-binding domains are highly conserved. The fact that the absence of both PDR1 and PDR3 (simultaneous disruption of the two genes) enhances multidrug sensitivity strongly suggests that the two transcriptional factors have closely related functions.
British journal of cancer, 1998
Identification and quantitative evaluation of drug resistance markers are essential to assess the impact of multidrug resistance (MDR) in clinical oncology. The MDR1 gene confers pleiotropic drug resistance in tumour cells, but other molecular mechanisms are also involved in drug resistance. In particular, the clinical pattern of expression of the other MDR-related genes is unclear and their interrelationships are still unknown. Here, we report standardization of the procedures used to determine a reliable method of semiquantitative reverse transcriptase polymerase chain reaction (RT-PCR) using a standard series of drug-sensitive and increasingly resistant cell lines to evaluate the expression of three MDR-related genes, i.e. MDR1 (multidrug resistance gene 1), MRP (multidrug resistance related protein) and GSTp (glutathione-S-transferase p), reported to be endogenous standard genes for normalization of mRNAs. A total of 74 breast cancer surgical biopsies, obtained before any treatm...
Cancer research, 1993
Two doxorubicin-selected human tumor cell lines, H69AR and HT1080/DR4, display a multidrug resistance phenotype but do not overexpress P-glycoprotein. Recently, a 6.5-kilobase mRNA encoding a novel member of the ATP-binding cassette superfamily of transport proteins, designated multidrug resistance-associated protein (MRP), has been identified in the H69AR cell line. In the present study, the levels of MRP mRNA were found to be 14-fold higher in HT1080/DR4 cells relative to sensitive HT1080 cells. Southern blotting indicates that gene amplification contributes to the overexpression of MRP in HT1080/DR4 cells. Using a 4-kilobase MRP complementary DNA probe, MRP genes were localized to 2-5 chromosomes bearing homogeneously staining regions and to multiple double minute chromosomes in H69AR cells. Resistant H69AR cells also contained a new der(16) with a structural aberration affecting 16p13.1, the normal cellular locus of the MRP gene. The MRP probe hybridized to two small homogeneous...