Upstream organization of and multiple transcripts from the human folylpoly-γ-glutamate synthetase gene

S. J. Freemantle, S. M. Taylor, G. Krystal, R. G. Moran

Research output: Contribution to journalArticlepeer-review

Abstract

Folylpoly-γ-glutamate synthetase (FPGS) is essential for the survival of proliferating mammalian cells and central to the action of all 'classical' folate antimetabolites. We report the isolation of cDNAs corresponding to the 5' ends of FPGS mRNA from both human and hamster cells which include a start codon upstream of and in-frame with the AUG in the previously reported FPGS open reading frame. The predicted hamster and human amino-terminal extension peptides have features consistent with a mitochondrial targeting sequence. Ribonuclease protection and 5'-rapid amplification of cDNA ends assays indicated multiple transcriptional start sites consistent with the sequence of the promoter region of this gone, which was highly GC-rich and did not contain TATA or CCAAT elements. These start sites would generate two classes of transcripts, one including the upstream AUG and one in which only the downstream AUG would be available for translation initiation. Transfection of the full length human cDNA into cells lacking FPGS restored their ability to grow in the absence of glycine, a product of mitochondrial folate metabolism, as well as of thymidine and purines. Therefore, we propose that the mitochondrial and cytosolic forms of FPGS are derived from the same gone, arising from the use of the two different translation initiation codons, and that the translation products differ by the presence of a 42-residue amino- terminal mitochondrial leader peptide.

Original languageEnglish (US)
Pages (from-to)9579-9584
Number of pages6
JournalJournal of Biological Chemistry
Volume270
Issue number16
DOIs
StatePublished - 1995

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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