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Journal of Virology, July 2007, p. 7149-7155, Vol. 81, No. 13
0022-538X/07/$08.00+0     doi:10.1128/JVI.00215-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Atypical bZIP Domain of Viral Transcription Factor Contributes to Stability of Dimer Formation and Transcriptional Function{triangledown}

Celine Schelcher,1 Salama Al Mehairi,1 Elizabeth Verrall,1 Questa Hope,1 Kirsty Flower,1 Beth Bromley,2 Derek N. Woolfson,2,3 Michelle J. West,1 and Alison J. Sinclair1*

School of Life Sciences, University of Sussex, Brighton BN1 9QG, United Kingdom,1 School of Chemistry, Cantock's Close, University of Bristol, Bristol BS8 1TS, United Kingdom,2 Department of Biochemistry, School of Medical Sciences, University of Bristol, Bristol BS8 1TD, United Kingdom3

Received 31 January 2007/ Accepted 18 April 2007

The Epstein-Barr virus transcription factor Zta (encoded by BZLF1) is a bZIP protein containing an {alpha}-helical coiled-coil homodimerization motif (zipper). The Zta zipper forms less-stable dimers than other bZIP proteins, and an adjacent region (CT) interacts with the zipper to form a novel structure that is proposed to strengthen the dimer. Here we question the role of the CT region for Zta function. Cross-linking experiments demonstrate that the entire CT region lies adjacent to the zipper. Detailed analyses of Zta truncation mutations identify an involvement of the proximal CT region (221 to 230) in dimer formation with a further contribution from the distal region (236 to 243). Biophysical analyses reveal that residues 221 to 230 enhance the stability of the coiled coil. The ability of the Zta truncation mutants to interact with three Zta-binding sites also requires the proximal CT region. Fine mapping of DNA-binding requirements highlighted the contribution of these amino acids for Zta function. Thus, the proximal part of the CT region is required to aid the dimerization of Zta and thereby its DNA-binding ability. In contrast, although the distal part of the CT region aids dimerization, it promotes only a modest increase in DNA binding. To probe this further, we defined the contribution from the CT region for Zta to transactivate a promoter embedded within the viral genome. From this we conclude that the proximal part of the CT region is absolutely required, whereas the distal part is dispensable.

* Corresponding author. Mailing address: School of Life Sciences, University of Sussex, Brighton BN1 9QG, United Kingdom. Phone: (44) 1273 678 194. Fax: (44) 1273 678 433. E-mail: a.j.sinclair{at}sussex.ac.uk

{triangledown} Published ahead of print on 25 April 2007.

Journal of Virology, July 2007, p. 7149-7155, Vol. 81, No. 13
0022-538X/07/$08.00+0     doi:10.1128/JVI.00215-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Heather, J., Flower, K., Isaac, S., Sinclair, A. J. (2009). The Epstein-Barr virus lytic cycle activator Zta interacts with methylated ZRE in the promoter of host target gene egr1. J. Gen. Virol. 90: 1450-1454 [Abstract] [Full Text]  
  • McDonald, C. M., Petosa, C., Farrell, P. J. (2009). Interaction of Epstein-Barr Virus BZLF1 C-Terminal Tail Structure and Core Zipper Is Required for DNA Replication but Not for Promoter Transactivation. J. Virol. 83: 3397-3401 [Abstract] [Full Text]  


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