MOLECULAR-CLONING OF THE HUMAN PLACENTAL FOLATE TRANSPORTER

We have isolated a cDNA clone from a human placental library which cod es for a functional folate transporter (hFOLT). An RT-PCR product obta ined from mouse intestinal mRNA using primers specific for the mouse f olate transporter cDNA was used to screen the cDNA library. The hFOLT cDNA predicts a protein of 590 amino acids with twelve potential trans membrane domains. The amino acid sequence has 65% identity to the mous e and hamster folate transporters. When transfected into COS-1 and HeL a cells, the hFOLT cDNA causes a significant increase in the uptake of 5-methyltetrahydrofolate. The mRNA transcripts hybridizing to the hFO LT cDNA are detectable in the placenta and liver and also in several c ell lines of human origin. The size of the principal transcript is 2.7 kb. This constitutes the first report on the cloning of a vitamin tra nsporter from a human tissue. (C) 1995 Academic Press, Inc.