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Journal of Virology, September 2009, p. 8733-8743, Vol. 83, No. 17
0022-538X/09/$08.00+0     doi:10.1128/JVI.00810-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Transient Expression of Herpes Simplex Virus Type 1 ICP22 Represses Viral Promoter Activity and Complements the Replication of an ICP22 Null Virus {triangledown}

J. Jason Bowman,{dagger} Joseph S. Orlando,§ David J. Davido,{ddagger} Anna S. Kushnir, and Priscilla A. Schaffer*

Departments of Medicine and Microbiology and Molecular Genetics, Program in Virology, Harvard Medical School at the Beth Israel Deaconess Medical Center, Boston, Massachusetts 02215

Received 21 April 2009/ Accepted 11 June 2009

Of the five herpes simplex virus type 1 immediate early (IE) proteins, the least is known about the function of ICP22 during productive infection and latency. Research characterizing the physical and functional properties of the protein has been limited because ICP22 has proven to be difficult to express in transient assays. In addition, genetic analysis of ICP22 has been complicated by the fact that the C terminus of ICP22 is expressed as a discrete protein product. In order to characterize properties of mutant and wild-type ICP22, we developed a transient expression system. We found that ICP22 can be expressed at detectable levels when placed under the control of the cytomegalovirus IE promoter, confirming recent observations by K. A. Fraser and S. A. Rice (J. Virol. 81:5091-5101, 2007). We extended this analysis to show that ICP22 can also be expressed from its own promoter in the presence of other viral factors, either by coexpression with ICP0 or by infection with an ICP22 null virus. Notably, infection of cells transfected with an ICP22 expression vector yielded ICP22 protein that was modified in a manner similar to that of ICP22 protein detected in wild-type-infected cells. We go on to demonstrate that the failure of ICP22 protein to be expressed in transiently transfected cells was not due to inactivity of the ICP22 promoter, but rather to the ability of ICP22 to inhibit expression of reporter gene activity, including its own, in transient assays. Of special note was the observation that expression of ICP22 was sufficient to prevent transactivation of reporter genes by ICP0. Finally, transient expression of ICP22 was sufficient to complement replication of an ICP22 null virus, demonstrating that this system can be used to study functional properties of ICP22. Collectively, this transient expression system facilitates tests of the physical and functional properties of ICP22 and ICP22 mutants prior to introduction of mutant genes into the viral genome.

* Corresponding author. Present address: Department of Molecular and Cellular Biology, University of Arizona, Life Sciences South Building, 1007 E. Lowell Street, P.O. Box 210106, Tucson, AZ 85721-0106. Phone: (520) 626-0106. Fax: (520) 621-3709. E-mail: pas{at}email.arizona.edu

{triangledown} Published ahead of print on 17 June 2009.

{dagger} Present address: 1 Blackfan Circle, Karp Family Research Building, Boston, MA 02115.

§ Present address: Millipore Corporation, 80 Ashby Rd., Bedford, MA 01730.

{ddagger} Present address: University of Kansas, 1200 Sunnyside Ave., 7047 Haworth Hall, Lawrence, KS 66045.

Present address: Harvard Medical School, 250 Longwood Ave., Department of Biological Chemistry and Molecular Pharmacology, Seeley G. Mudd Rm 309, Boston, MA 02115.

Journal of Virology, September 2009, p. 8733-8743, Vol. 83, No. 17
0022-538X/09/$08.00+0     doi:10.1128/JVI.00810-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Bowman, J. J., Schaffer, P. A. (2009). Origin of Expression of the Herpes Simplex Virus Type 1 Protein US1.5. J. Virol. 83: 9183-9194 [Abstract] [Full Text]  


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