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Journal of Virology, September 2007, p. 9230-9237, Vol. 81, No. 17
0022-538X/07/$08.00+0     doi:10.1128/JVI.01054-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

DNA-Dependent Oligomerization of Herpes Simplex Virus Type 1 Regulatory Protein ICP4{triangledown}

Ruhul H. Kuddus{dagger} and Neal A. DeLuca*

Department of Molecular Genetics and Biochemistry, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261

Received 15 May 2007/ Accepted 13 June 2007

The human herpes simplex virus type 1 regulatory protein ICP4 binds DNA as a dimer and forms a single protein-DNA complex (A complex) with short DNA probes. ICP4 oligomerized in a DNA-dependent manner, forming two or more protein-DNA complexes with longer DNA fragments containing a single DNA binding site. When resolved electrophoretically, one or more low-mobility DNA-protein complexes follow the fast-moving A complex. The major protein-DNA complex (B complex) formed by ICP4 with long DNA probes migrates just behind the A complex in the electric field, implying the oligomerization of ICP4 on the DNA. Binding experiments with circularly permutated DNA probes containing one ICP4 binding site revealed that about 70 bp of nonspecific DNA downstream of the cognate ICP4 binding site was required for efficient B complex formation. In addition, the C-terminal domain of ICP4 was found to be required for DNA-dependent oligomerization and B complex formation. Gel mobility shift analysis of protein-DNA complexes, combined with supershift analysis using different monoclonal antibodies, indicated that the B complex contained two ICP4 dimers. DNase I footprinting of ICP4-DNA complexes showed that one ICP4 dimer contacts the specific binding site and another ICP4 dimer contacts nonspecific DNA in the B complex. DNA-dependent oligomerization increased the affinity of ICP4 for relatively weak binding sites on large DNA molecules. The results of this study suggest how ICP4 may use multiple weak binding sites to aid in transcription activation.

* Corresponding author. Mailing address: E1257 Biomedical Science Tower, Department of Molecular Genetics and Biochemistry, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261. Phone: (412) 648-9947. Fax: (421) 624-1401. E-mail: ndeluca{at}pitt.edu

{triangledown} Published ahead of print on 20 June 2007.

{dagger} Present address: Department of Biology, Utah Valley State College, Orem, UT 84058.

Journal of Virology, September 2007, p. 9230-9237, Vol. 81, No. 17
0022-538X/07/$08.00+0     doi:10.1128/JVI.01054-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Livingston, C. M., DeLuca, N. A., Wilkinson, D. E., Weller, S. K. (2008). Oligomerization of ICP4 and Rearrangement of Heat Shock Proteins May Be Important for Herpes Simplex Virus Type 1 Prereplicative Site Formation. J. Virol. 82: 6324-6336 [Abstract] [Full Text]  
  • Sampath, P., DeLuca, N. A. (2008). Binding of ICP4, TATA-Binding Protein, and RNA Polymerase II to Herpes Simplex Virus Type 1 Immediate-Early, Early, and Late Promoters in Virus-Infected Cells. J. Virol. 82: 2339-2349 [Abstract] [Full Text]  


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