Abstract
The reduced folate carrier gene (rfc) encodes a putative protein that is involved in the intracellular accumulation of folates. In this report, we describe the organization of the rfc gene from Chinese hamster ovary cells. The hamster rfc gene contains 7 exons and 6 introns, which span 15.3 kilobases. It codes for two alternatively spliced messenger RNAs, one that contains all 7 exons and one that lacks exon 2 but contains the remaining 6 exons. The transcriptional start of the gene has been mapped to six sites approximately 200 base pairs upstream of the putative ATG initiation codon. The promoter region has no TATA box-like sequence but contains a consensus Sp1 binding site. This is the first report of the genomic structure of the reduced folate carrier gene from any species.
Highlights
We have previously described the isolation of both a hamster genomic DNA cosmid clone [29] and a cDNA clone [28] that can, upon transfection, complement mutant Chinese hamster ovary (CHO) cell lines that are unable to take up folates
The present study describes the organization of the hamster rfc gene, the identification of two alternatively spliced mRNA isoforms, and the mapping of the transcriptional start site
Amplification of the hamster rfc gene using first-strand cDNA synthesized from ProϪ3 cells confirmed the presence of two mRNA species that differed in size by 121 bp (Fig. 3B)
Summary
The intracellular accumulation of folic acid and reduced folates is essential for the survival of mammalian cells. Folate-binding protein has a high affinity for folic acid and a low affinity for reduced folates including the chemotherapeutic agent methotrexate (Mtx)1 [1,2,3,4,5,6,7,8]. The cDNA encoding folate-binding protein has been cloned from various sources (9 –14), and its genomic structure has been determined [15,16,17]. The second system consists of a 36 –78-kDa glycoprotein termed the reduced folate carrier, which has a higher affinity for reduced folates including Mtx and a lower affinity for folic acid (18 –22). Several cDNAs that putatively encode the reduced folate carrier have recently been cloned from human [23,24,25,26], mouse [27], and hamster [28] cells. The nucleotide sequence(s) reported in this paper has been submitted to the GenBankTM/EBI Data Bank with accession number(s) U58838 and U58839
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
