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Hypoxia actively represses transcription by inducing negative cofactor 2 (Dr1/DrAP1) and blocking preinitiation
Nicholas Denko1, Kara Wernke-Dollries, Amber Buescher Johnson
1Department of Radiation Oncology, Division of Radiation and Cancer Biology, Stanford University Medical School, Stanford, California 94305-5152, USA.
The Journal of Biological Chemistry
|December 13, 2002
Summary
Hypoxic stress actively represses gene transcription by preventing preinitiation complex assembly. This is mediated by negative cofactor 2 (NC2) protein binding, offering insights into cellular energy conservation during low-oxygen conditions.
Area of Science:
- Molecular Biology
- Cellular Stress Response
- Gene Regulation
Background:
- Hypoxia, a state of low oxygen, is a significant stressor linked to various diseases.
- Hypoxic stress influences cellular processes, including gene expression, through both activation and repression.
- Understanding the mechanisms of hypoxic gene regulation is crucial for disease research.
Purpose of the Study:
- To investigate the molecular mechanisms behind hypoxia-mediated transcriptional repression.
- To determine how cells selectively repress gene transcription under hypoxic conditions.
- To identify key protein factors involved in regulating gene expression during hypoxia.
Main Methods:
- In vitro reconstitution of the bimodal hypoxic response.
- Analysis of preinitiation complex (PIC) assembly in hypoxic cell extracts.
- Investigation of RNA polymerase II C-terminal domain (CTD) phosphorylation.
- Immunodepletion assays to assess the role of negative cofactor 2 (NC2) protein.
Main Results:
- Hypoxic cell extracts showed impaired preinitiation complex assembly at specific promoters, while transcript elongation remained functional.
- Hypoxia-induced binding of negative cofactor 2 (NC2) protein (alpha/beta, Dr1/DrAP1) to core promoters blocked PIC assembly and CTD phosphorylation.
- Depletion of NC2 protein complexes restored transcription repressed by hypoxia, without affecting normoxic transcription.
Conclusions:
- Negative cofactor 2 (NC2) plays a critical role in mediating hypoxia-induced transcriptional repression.
- NC2 binding to promoters is a key mechanism for selective gene silencing under hypoxic stress.
- Regulation of NC2 activity represents a potential cellular strategy for energy conservation during hypoxia.