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Binding of Upstream Stimulatory Factor and a Cell-specific Activator to the Calcitonin/Calcitonin Gene-related Peptide Enhancer
Journal article   Open access   Peer reviewed

Binding of Upstream Stimulatory Factor and a Cell-specific Activator to the Calcitonin/Calcitonin Gene-related Peptide Enhancer

Thomas M Lanigan and Andrew F Russo
The Journal of biological chemistry, Vol.272(29), pp.18316-18324
07/18/1997
DOI: 10.1074/jbc.272.29.18316
PMID: 9218472
url
https://doi.org/10.1074/jbc.272.29.18316View
Published (Version of record) Open Access

Abstract

The calcitonin/calcitonin gene-related peptide (CT/CGRP) gene is selectively transcribed in thyroid C cells and neurons. We have previously shown that the rat CT/CGRP cell-specific enhancer is synergistically regulated by a helix-loop-helix (HLH) protein and the OB2 octamer-binding protein. In this report, we show that the HLH-OB2 enhancer is required for full promoter activity, even in the context of other HLH elements. Since this enhancer appears to be a major controlling element, we have characterized the HLH and OB2 DNA binding proteins. We have identified the major HLH complex as a heterodimer of the ubiquitous upstream stimulatory factor (USF)-1 and USF-2 proteins. USF bound the enhancer with a reasonably high affinity (KD 1.6 nM), comparable to other genes. Characterization of a series of mutations revealed that a portion of the HLH motif is also recognized by OB2 and confirmed that HLH activity requires OB2. We have shown that OB2 is a single DNA binding protein based on UV cross-linking studies. The 68-kDa protein-DNA complex was detected only in C cell lines, including a human C cell line that has robust HLH-OB2 enhancer activity. These results suggest that the calcitonin/CGRP gene is controlled by the combinatorial activity of a ubiquitous USF HLH heterodimer and an associated cell-specific activator.

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