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Identification of a pH‐responsive DNA region upstream of the transcription start site of human NBCe1‐B
Author(s) -
Snead Christian M.,
Smith Susan M.,
Sadeghein Negar,
Lacruz Rodrigo S.,
Hu Ping,
Kurtz Ira,
Paine Michael L.
Publication year - 2011
Publication title -
european journal of oral sciences
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.802
H-Index - 93
eISSN - 1600-0722
pISSN - 0909-8836
DOI - 10.1111/j.1600-0722.2011.00867.x
Subject(s) - microbiology and biotechnology , enhancer , chemistry , transcription factor , gene , transcription (linguistics) , binding site , ameloblast , dna , biology , enamel paint , biochemistry , medicine , linguistics , philosophy , dentistry
Snead CM, Smith SM, Sadeghein N, Lacruz RS, Hu P, Kurtz I, Paine ML. Identification of a pH‐responsive DNA region upstream of the transcription start site of human NBCe1‐B.
Eur J Oral Sci 2011; 119 (Suppl. 1): 136–141. © 2011 Eur J Oral Sci 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 an increase of ∼ 2.3‐fold in gene‐transcription activity when transfected into ameloblast‐like cells and cultured in medium maintained at pH 6.8 (vs. pH 7.4). 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.