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Negative regulatory elements in the human parathyroid hormone gene.
T Okazaki1, J D Zajac, T Igarashi
1Endocrine Unit, Massachusetts General Hospital, Boston.
The Journal of Biological Chemistry
|November 15, 1991
Summary
Researchers found upstream DNA elements that suppress human parathyroid hormone (hPTH) gene transcription. Nuclear factors bind these elements, reducing gene expression in cultured cells, revealing novel regulatory mechanisms.
Area of Science:
- Molecular Biology
- Genetics
- Gene Regulation
Background:
- The human parathyroid hormone (hPTH) gene's transcriptional regulation is complex.
- Understanding negative regulatory elements is crucial for comprehending gene expression control.
Purpose of the Study:
- To identify and characterize upstream negative regulatory elements of the hPTH gene.
- To investigate the role of nuclear factors in hPTH gene suppression.
Main Methods:
- Plasmid construction with varying lengths of the hPTH 5'-flanking region linked to a reporter gene (chloramphenicol acetyltransferase - CAT).
- Transfection of cultured cells with these plasmids to assess CAT activity.
- Deletion analysis to pinpoint regulatory regions.
- Nuclear factor binding assays.
Main Results:
- A 4.7 kilobase pair upstream region of the hPTH gene significantly reduced CAT activity (to 10%) compared to a 684 base pair region.
- Deletion analyses identified at least two distinct upstream DNA elements responsible for negative regulation.
- Nuclear factors were found to specifically bind to DNA sequences within these negative regulatory elements.
- These DNA-binding interactions correlated with the suppression of hPTH gene transcription.
Conclusions:
- The hPTH gene is subject to negative regulation by upstream DNA elements located far from the transcription start site.
- Specific nuclear factors bind to these elements, mediating transcriptional suppression.
- These findings reveal novel mechanisms of hPTH gene regulation involving distal negative control elements.