| First Author | Tse A | Year | 1998 |
| Journal | J Biol Chem | Volume | 273 |
| Issue | 40 | Pages | 25953-60 |
| PubMed ID | 9748272 | Mgi Jnum | J:50354 |
| Mgi Id | MGI:1303207 | Doi | 10.1074/jbc.273.40.25953 |
| Citation | Tse A, et al. (1998) Mutations in the reduced folate carrier gene which confer dominant resistance to 5,10-dideazatetrahydrofolate. J Biol Chem 273(40):25953-60 |
| abstractText | L1210/D3 mouse leukemia cells are resistant to 5, 10-dideazatetrahydrofolate due to expansion of cellular folate pools which block polyglutamation of the drug (Tse, A, and Moran, RG. (1998) J Biol Chem 273, 25944-25952). These cells were found to have two point mutations in the reduced folate carrier (RFC), resulting in a replacement of isoleucine 48 by phenylalanine and of tryptophan 105 by glycine. Each mutation contributes to the resistance phenotype. Genomic DNA from resistant cells contained both the wild-type and mutant alleles, but wild-type message was not detected. Folic acid was a much better substrate, and 5-formyltetrahydrofolate was a poorer substrate for transport in L1210/D3 cells relative to L1210 cells. Enhanced transport of folic acid was due to a marked, approximately 20-fold, decrease in the influx Km. Influx of methotrexate and 5,10-dideazatetrahydrofolate were minimally altered. Transfection of mutated rfc cDNA into RFC-null L1210/A cells produced the substrate specificity and 5, 10-dideazatetrahydrofolate resistance observed in the L1210/D3 line. Transfection of the mutant cDNA into wild-type cells also conferred resistance to 5,10-dideazatetrahydrofolate. We conclude that the I48F and W105G mutations in RFC caused resistance to 5, 10-dideazatetrahydrofolate, that the region of the RFC protein near these two positions defines the substrate-binding site, that the wild-type allele was silenced during the multistep development of resistance, and that this mutant phenotype represents a genetically dominant trait. |
