Identification of a pH-responsive DNA region upstream of the transcription start site of human NBCe1-B

Christian M. Snead, Susan M. Smith, Negar Sadeghein, Rodrigo S. Lacruz, Ping Hu, Ira Kurtz, Michael L. Paine

Research output: Contribution to journalArticlepeer-review


In rodent incisors two distinct stages of enamel formation can be identified visually based on cell morphology: the secretory stage and the maturation stage. The expression profiles of many genes characterize both stages, including the bicarbonate transport protein NBCe1. Bicarbonate is a requirement for the mineralizing enamel matrix to buffer excessive protons that form as a consequence of hydroxyapatite formation. NBCe1-B mRNA is up-regulated during the maturation stage of amelogenesis, where hydroxyapatite formation predominates. In this study, a presumed 572-bp NBCe1-B promoter region was subcloned into a reporter construct, and within this 572-bp region of DNA we characterized a 285-bp segment that shows anincrease of ~2.3-fold in gene-transcription activity when transfected into ameloblast-like cells and cultured in medium maintained at pH6.8 (vs. pH7.4). A presumed pH-responsive transcriptional factor-binding domain(s) thus resides in the 285-bp NBCe1-B promoter region where candidate domains include the nuclear factor of kappa light polypeptide gene enhancer in B-cells1(NFKB1), jun proto-oncogene (JUN), and tumor protein p53(TP53)-binding sites. Mutagenesis studies identify that both the NFKB1- and TP53-binding sites are responsive to changes in the extracellular pH. These data help to explain how ameloblasts respond to the altered extracellular milieu of protons by changing their gene-expression profile throughout the stages of amelogenesis.

Original languageEnglish (US)
Pages (from-to)136-141
Number of pages6
JournalEuropean Journal of Oral Sciences
Issue numberSUPPL.1
StatePublished - Dec 2011


  • Enamel
  • Mineralization
  • PH regulation
  • PH sensing
  • Sodium bicarbonate transporter

ASJC Scopus subject areas

  • General Dentistry


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