Transcription of the mouse RFC-1 gene encoding a folate transporter. Multiplicity and properties of promoters with minimum requirements for their basal activity Journal Article

Authors: Tolner, B.; Singh, A.; Esaki, T.; Roy, K.; Sirotnak, F. M.
Article Title: Transcription of the mouse RFC-1 gene encoding a folate transporter. Multiplicity and properties of promoters with minimum requirements for their basal activity
Abstract: The mouse RFC-1 gene incorporates alternates of exon 1 (exon 1 and la) which encode different 5' ends. This finding, and the elucidation of a promoter-like sequence immediately upstream of these alternates of exon 1, suggest that two separate promoters drive transcription of this gene. The regions upstream of either exon 1 or exon la inserted in pGL3 will separately promote transcription in NIH3T3 cells of the luciferase reporter gene, with the region upstream of exon 1 having the strongest promoter activity. Tissue- specific expression in the form of RFC-1 mRNA splice variants reflects the separate action of each promoter. In the most upstream portion of the region proximal to exon 1a, elements were revealed that enhance transcription along with a more downstream element that suppresses transcription in NIH3T3 cells. Three Sp1 sites closely proximal to exon 1a within a region spanning 123 nucleotides were shown to be transcriptionally active by site-directed mutagenesis, with the middle SP1 site found to be the most important of the three in maintaining basal promoter activity. A poly (GT) 21 di-nucleotide repetitive element upstream of these Sp1 sites was found in a region which, when deleted, increased transcription. In the region upstream of exon 1, two elements were elucidated which enhanced transcription. Site-directed mutagenesis showed that two adjacent SP1 sites proximal to exon 1 were equally important in sustaining basal promoter activity. The role of each Sp1 site in maintaining basal activity of each promoter was confirmed by DNase I footprinting analysis. In addition, a binding site of unknown significance was identified by this analysis within the upstream promoter sequence between the two Sp1 sites proximal to exon 1a. These data show that both promoters regulating expression of the RFC-1 gene utilize closely spaced Sp1 sites in tandem to sustain basal transcription, at least in NIH3T3 cells, in a manner characteristic of TATA-less promoters.
Keywords: gene sequence; promoter region; exon; sequence deletion; nonhuman; animal cell; mouse; animals; mice; luciferase; membrane proteins; genetic transcription; transcription, genetic; hela cells; animalia; gene expression regulation; dna; molecular sequence data; messenger rna; rna, messenger; carrier proteins; transcription factor sp1; murinae; reporter gene; base sequence; mutagenesis, site-directed; genes, reporter; folic acid; rodentia; luciferases; site directed mutagenesis; cell strain 3t3; nucleotide repeat; 3t3 cells; nucleotide; tata box; membrane transport proteins; dna footprinting; promoter regions (genetics); deoxyribonuclease i; humans; priority journal; article; folate transport; murine rfc-1 promoters
Journal Title: Gene
Volume: 231
Issue: 1-2
ISSN: 0378-1119
Publisher: Elsevier Science, Inc.  
Date Published: 1999-04-29
Start Page: 163
End Page: 172
Language: English
DOI: 10.1016/s0378-1119(99)00078-5
PUBMED: 10231581
PROVIDER: scopus
Notes: Article -- Export Date: 16 August 2016 -- Source: Scopus