Jun 22, 1993

Altered folate-binding protein mRNA stability in KB cells grown in folate-deficient medium

Biochemical Pharmacology
C T Hsueh, B J Dolnick


Folate-binding protein (FBP), a high-affinity folate receptor, is responsible for cellular accumulation of folate and folate analogs such as methotrexate in human KB (nasopharyngeal carcinoma) cells. Both FBP and FBP mRNA increase 3- to 5-fold when KB cells are grown in folate-deficient (less than 10 nM folate) medium (KB-FD), compared with growth in standard folate-replete medium containing at least 2 microM folate (KB-FR). The possible mechanisms of enhanced FBP gene expression in KB-FD were examined in this study. Southern blot analysis revealed no significant change in the FBP gene organization or copy number in the KB-FD DNA. While hypomethylation of the FBP gene was observed in KB-FD DNA, relative to KB-FR DNA, exposure of KB-FR to the DNA methylation inhibitors did not result in elevated FBP mRNA levels. The transcriptional rate of the FBP gene was the same in KB-FR and KB-FD. RNA half-life studies indicated that the half-life of FBP mRNA in KB-FD was increased approximately 2.5-fold, compared with KB-FR. Thus, the increase in the steady-state levels of FBP mRNA in KB-FD can be attributed partly to increased FBP mRNA stability.

  • References29
  • Citations18


  • References29
  • Citations18


Mentioned in this Paper

Nasopharyngeal Carcinoma
DNA Methylation [PE]
Dysautonomia, Familial
Hormone Receptors, Cell Surface
Transcription, Genetic
DNA Methylation
Folate receptor
Gene Expression
Binding Protein

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