| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
,
* Department of Laboratory Medicine and Pathobiology and
Department of Medical Biophysics, University of Toronto, Toronto, Canada; and
Renal Division and Department of Medicine, St. Michael’s Hospital and University of Toronto, Toronto, Canada
A marked difference exists in the inducibility of inducible NO synthase (iNOS) between humans and rodents. Although important cis and trans factors in the murine and human iNOS promoters have been characterized using episomal-based approaches, a compelling molecular explanation for why human iNOS is resistant to induction has not been reported. In this study we present evidence that the hyporesponsiveness of the human iNOS promoter is based in part on epigenetic silencing, specifically hypermethylation of CpG dinucleotides and histone H3 lysine 9 methylation. Using bisulfite sequencing, we demonstrated that the iNOS promoter was heavily methylated at CpG dinucleotides in a variety of primary human endothelial cells and vascular smooth muscle cells, all of which are notoriously resistant to iNOS induction. In contrast, in human cell types capable of iNOS induction (e.g., A549 pulmonary adenocarcinoma, DLD-1 colon adenocarcinoma, and primary hepatocytes), the iNOS promoter was relatively hypomethylated. Treatment of human cells, such as DLD-1, with a DNA methyltransferase inhibitor (5-azacytidine) induced global and iNOS promoter DNA hypomethylation. Importantly, 5-azacytidine enhanced the cytokine inducibility of iNOS. Using chromatin immunoprecipitation, we found that the human iNOS promoter was basally enriched with di- and trimethylation of H3 lysine 9 in endothelial cells, and this did not change with cytokine addition. This contrasted with the absence of lysine 9 methylation in inducible cell types. Importantly, chromatin immunoprecipitation demonstrated the selective presence of the methyl-CpG-binding transcriptional repressor MeCP2 at the iNOS promoter in endothelial cells. Collectively, our work defines a role for chromatin-based mechanisms in the control of human iNOS gene expression.
This article has been cited by other articles:
|
|
 |
|
  C. C. Matouk and P. A. Marsden Epigenetic Regulation of Vascular Endothelial Gene Expression Circ. Res., April 25, 2008; 102(8): 873 - 887. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 Y. Zhang, V. Brovkovych, S. Brovkovych, F. Tan, B.-S. Lee, T. Sharma, and R. A. Skidgel Dynamic Receptor-dependent Activation of Inducible Nitric-oxide Synthase by ERK-mediated Phosphorylation of Ser745 J. Biol. Chem., November 2, 2007; 282(44): 32453 - 32461. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 D. M.E.I. Hellebrekers, V. Melotte, E. Vire, E. Langenkamp, G. Molema, F. Fuks, J. G. Herman, W. Van Criekinge, A. W. Griffioen, and M. van Engeland Identification of Epigenetically Silenced Genes in Tumor Endothelial Cells Cancer Res., May 1, 2007; 67(9): 4138 - 4148. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 Z. Guo, L. Shao, Q. Du, K. S. Park, and D. A. Geller Identification of a classic cytokine-induced enhancer upstream in the human iNOS promoter FASEB J, February 1, 2007; 21(2): 535 - 542. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 C.-H. Leung, S. P. Grill, W. Lam, W. Gao, H.-D. Sun, and Y.-C. Cheng Eriocalyxin B Inhibits Nuclear Factor-{kappa}B Activation by Interfering with the Binding of Both p65 and p50 to the Response Element in a Noncompetitive Manner Mol. Pharmacol., December 1, 2006; 70(6): 1946 - 1955. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. Liu, M. Mendicino, Q. Ning, A. Ghanekar, W. He, I. McGilvray, I. Shalev, D. Pivato, D. A. Clark, M. J. Phillips, et al. Cytokine-Induced Hepatic Apoptosis Is Dependent on FGL2/Fibroleukin: The Role of Sp1/Sp3 and STAT1/PU.1 Composite cis Elements. J. Immunol., June 1, 2006; 176(11): 7028 - 7038. [Abstract] [Full Text] [PDF]
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
