Related Experiment Video

Updated: Aug 30, 2026

Induction and Testing of Hypoxia in Cell Culture
07:01

Induction and Testing of Hypoxia in Cell Culture

Published on: August 12, 2011

Cyclin dependent kinase inhibitor p27(Kip1) is upregulated by hypoxia via an ARNT dependent pathway

Gang Wang1, Richard Reisdorph, Robert E Clark

  • 1Division of Basic Biomedical Sciences, School of Medicine, University of South Dakota, Vermillion, South Dakota 57069, USA.

Journal of Cellular Biochemistry
|October 3, 2003
PubMed

Insights

Hypoxia affects cyclin-dependent kinase inhibitor p27(Kip1) expression differently in cells based on aryl hydrocarbon receptor nuclear translocator (ARNT) presence. ARNT mediates hypoxia-induced p27(Kip1) gene upregulation in hepatoma cells.

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Cancer Research

Background:

  • The cyclin-dependent kinase (Cdk) inhibitor p27(Kip1) regulates cell cycle progression from G(1) to S phase.
  • p27(Kip1) plays a role in cellular responses to hypoxia, but the regulatory mechanisms remain unclear.
  • Aryl hydrocarbon receptor nuclear translocator (ARNT) is a key transcription factor involved in cellular responses to various stimuli.

Purpose of the Study:

  • To investigate the role of ARNT in the hypoxia-induced regulation of p27(Kip1) expression.
  • To compare p27(Kip1) expression under hypoxic conditions in ARNT-proficient and ARNT-deficient murine hepatoma cell lines.
  • To elucidate the molecular mechanisms underlying hypoxia-mediated p27(Kip1) regulation.

Main Methods:

  • Comparative analysis of p27(Kip1) expression in Hepa-1 (ARNT-proficient) and c4 (ARNT-deficient) murine hepatoma cell lines under hypoxia.
  • Stable transfection of c4 cells with the wild-type ARNT gene.
  • Assessment of p27(Kip1) protein and mRNA levels under varying oxygen conditions and ARNT expression.

Main Results:

  • Hypoxia enhanced p27(Kip1) protein levels in Hepa-1 cells but reduced them in c4 cells.
  • Hypoxia-induced, ARNT-mediated transactivation of the p27(Kip1) gene was responsible for increased p27(Kip1) protein in Hepa-1 cells.
  • Restoration of ARNT in c4 cells led to hypoxia-induced p27(Kip1) mRNA increase and blocked the hypoxia-induced protein reduction.

Conclusions:

  • ARNT is a critical mediator in the transcriptional upregulation of the p27(Kip1) gene under hypoxic conditions.
  • ARNT-dependent regulation of p27(Kip1) influences cellular responses to hypoxia.
  • These findings highlight a novel mechanism of p27(Kip1) regulation in cancer cells facing hypoxic stress.

More Related Videos

Co-immunoprecipitation Assay Using Endogenous Nuclear Proteins from Cells Cultured Under Hypoxic Conditions09:17

Co-immunoprecipitation Assay Using Endogenous Nuclear Proteins from Cells Cultured Under Hypoxic Conditions

Published on: August 2, 2018

Related Concept Videos

Regulation of Angiogenesis and Blood Supply01:24

Regulation of Angiogenesis and Blood Supply

Rapidly dividing tumors, embryos, and wounded tissues require more oxygen than usual, lowering the oxygen concentration in the blood. At low oxygen or hypoxic conditions, an oxygen-sensitive transcription factor called the hypoxia-inducible factor 1 or HIF1 is activated. HIF1 is a dimeric protein of alpha (ɑ) and beta (β) subunits.  Under optimal oxygen conditions, HIF1β is present in the nucleus while HIF1ɑ remains in the cytosol. HIF1ɑ is hydroxylated by prolyl hydroxylase and factor...
Inhibition of Cdk Activity02:34

Inhibition of Cdk Activity

The orderly progression of the cell cycle depends on the activation of Cdk protein by binding to its cyclin partner. However, the cell cycle must be restricted when undergoing abnormal changes. Most cancers correlate to the deregulated cell cycle, and since Cdks are a central component of the cell cycle, Cdk inhibitors are extensively studied to develop anticancer agents. For instance, cyclin D associates with several Cdks, such as Cdk 4/6, to form an active complex. The cyclin D-Cdk4/6 complex...
PI3K/mTOR/AKT Signaling Pathway01:22

PI3K/mTOR/AKT Signaling Pathway

The mammalian target of rapamycin  (mTOR) is a serine/threonine kinase that regulates growth, proliferation, and cell survival in response to hormones, growth factors, or nutrient availability. This kinase exists in two structurally and functionally distinct forms: mTOR complex 1  (mTORC1) and mTOR complex 2  (mTORC2). The first form (mTORC1) is composed of a rapamycin-sensitive Raptor and proline-rich Akt substrate, PRAS40. In contrast,  mTORC2 consists of a rapamycin-insensitive companion...
Interactions Between Signaling Pathways01:19

Interactions Between Signaling Pathways

Signaling cascades usually lack linearity. Multiple pathways interact and regulate one another, allowing cells to integrate and respond to diverse environmental stimuli.
Convergence and divergence, and cross-talk between signaling pathways
Two distinct signaling pathways can converge on a single functional unit, which may either be a single protein or a complex of proteins. The response is either functionally distinct or synergistic between the two pathways but different from the response...
Adaptive Mechanisms in Cancer Cells02:53

Adaptive Mechanisms in Cancer Cells

Cancer cells accumulate genetic changes at an abnormally rapid rate due to the defects in the DNA repair mechanisms. From an evolutionary perspective, such genetic instability is advantageous for cancer development. Mutant cell lines accumulate a series of beneficial mutations that contribute to their progression into cancer.
Some of the advantages that cancer cells have on normal cells include - enhanced ability to divide without terminally differentiating, induce new blood vessel formation,...
mTOR Signaling and Cancer Progression03:03

mTOR Signaling and Cancer Progression

The mammalian target of rapamycin or mTOR protein was discovered in 1994 due to its direct interaction with rapamycin. The protein gets its name from a yeast homolog called TOR. The mTOR protein complex in mammalian cells plays a major role in balancing anabolic processes such as the synthesis of proteins, lipids, and nucleotides and catabolic processes, such as autophagy in response to environmental cues, such as availability of nutrients and growth factors.
The mTOR pathway or the...