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Journal of Virology, September 2009, p. 8409-8417, Vol. 83, No. 17
0022-538X/09/$08.00+0     doi:10.1128/JVI.00796-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Host Cell Detection of Noncoding Stuffer DNA Contained in Helper-Dependent Adenovirus Vectors Leads to Epigenetic Repression of Transgene Expression {triangledown}

P. Joel Ross,1,2,{dagger} Michael A. Kennedy,1,2 and Robin J. Parks1,2,3*

Regenerative Medicine Program, Ottawa Health Research Institute,1 Department of Biochemistry, Microbiology, and Immunology and Centre for Neuromuscular Disease,2 Department of Medicine, University of Ottawa, Ottawa, Ontario, Canada3

Received 20 April 2009/ Accepted 5 June 2009

Helper-dependent adenovirus (hdAd) vectors have shown great promise as therapeutic gene delivery vehicles in gene therapy applications. However, the level and duration of gene expression from hdAd can differ considerably depending on the nature of the noncoding stuffer DNA contained within the vector. For example, an hdAd containing 22 kb of prokaryotic DNA (hdAd-prok) expresses its transgene 60-fold less efficiently than a similar vector containing eukaryotic DNA (hdAd-euk). Here we have determined the mechanistic basis of this phenomenon. Although neither vector was subjected to CpG methylation and both genomes associated with cellular histones to similar degrees, hdAd-prok chromatin was actively deacetylated. Insertion of an insulator element between the transgene and the bacterial DNA derepressed hdAd-prok, suggesting that foreign DNA nucleates repressive chromatin structures that spread to the transgene. We found that Sp100B/Sp100HMG and Daxx play a role in repressing transgene expression from hdAd and act independently of PML bodies. Thus, we have identified nuclear factors involved in recognizing foreign DNA and have determined the mechanism by which associated genes are repressed.

* Corresponding author. Mailing address: Regenerative Medicine Program, Ottawa Health Research Institute, 501 Smyth Road, Ottawa, Ontario, Canada K1H 8L6. Phone: (613) 737-8123. Fax: (613) 737-8803. E-mail: rparks{at}ohri.ca

{triangledown} Published ahead of print on 10 June 2009.

{dagger} Present address: Department of Neurosciences and Mental Health, The Hospital for Sick Children, Toronto, Ontario, Canada.

Journal of Virology, September 2009, p. 8409-8417, Vol. 83, No. 17
0022-538X/09/$08.00+0     doi:10.1128/JVI.00796-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





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