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IMMUNOHISTOCHEMICAL DOUBLE-STAINING FOR AH RECEPTOR AND ARNT IN HUMAN EMBRYONIC PALATAL SHELVES
Citation:
Abbott, B., M. Probst, AND G. Perdew. IMMUNOHISTOCHEMICAL DOUBLE-STAINING FOR AH RECEPTOR AND ARNT IN HUMAN EMBRYONIC PALATAL SHELVES. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/J-95/152.
Description:
The aryl hydrocarbon receptor (AhR) and the AhR nuclear translocation protein (ARNT) are helix-loop-helix (HLH) proteins involved in transcriptional regulation. olycyclic aromatic halogenated chemicals, of which 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is the most potent, bind to the AhR. n the cellular cytoplasm, the AhR exists as a complex with the heat shock protein HSP90 and other small peptides. his complex dissociates following ligand binding and then the ligand-bound AhR binds ARNT. he ligand-AhR-ARNT complex interacts with a specific, nuclear DNA sequence, the xenobiotic response element (XRE), altering transcription of a regulated gene. tudies in hepatoma cell lines indicate that both proteins are required for regulation of transcription. n this study, AhR and ARNT were localized immunohistochemically in human embryonic palatal cells and specific patterns of expression were seen for each protein. ouble-staining protocol revealed that epithelial cells expressed both AhR and ARNT, but in mesenchyme and nasal spine cartilage individual cells were identified which expressed only AhR or ARNT. his heterogeneous pattern suggests that as yet unidentified helix-loop-helix partners for these proteins may exist. t is also possible that variations of the XRE sequence are available to bind these hybrid pairs. he heterogeneous expression pattern may also reflect a complex role for these HLH proteins as transcriptional regulators of embryonic development.