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Journal of Virology, January 1999, p. 214-224, Vol. 73, No. 1
Department of Biology, Elizabethtown College,
Elizabethtown, Pennsylvania 17022,1 and
Department of Microbiology and Immunology, Pennsylvania
State University College of Medicine, Hershey, Pennsylvania
170332
Received 30 January 1998/Accepted 18 September 1998
Simian virus 40 large-T antigen transactivates the ribosomal genes
which are transcribed by RNA polymerase (pol I), as well as genes that
are dependent on either pol II or pol III. This report identifies
regions and activities of T antigen that are required to transactivate
a pol I-dependent rat ribosomal gene promoter. By using the rat
ribosomal gene (rDNA) promoter linked to a chloramphenicol
acetyltransferase gene, we show that at least three separable T-antigen
regions are necessary to achieve wild-type levels of transactivation of
rDNA in transiently transfected monkey cells. One activity depends on
the region of T antigen shared with small-t antigen (T/t common
region). A second activity maps to amino acids 109 to 626 and is highly
sensitive to mutational inactivation. Complementation analyses suggest
that at least one activity in this region is independent of
and must be in cis with the activity within the T/t common
region. In addition, a functional nuclear localization signal is
required for maximal T-antigen-mediated transactivation of rat rDNA.
The three activities work in concert to override cellular
species-specific controls and transactivate the rat ribosomal gene
promoter. Finally, we provide evidence that although the tumor
suppressor protein Rb has been shown to repress a pol I-dependent
promoter, transactivation of the rat rDNA promoter does not depend on T
antigen's ability to bind the tumor suppressor product Rb.
0022-538X/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Transactivation of a Ribosomal Gene by Simian Virus 40 Large-T
Antigen Requires at Least Three Activities of the Protein
*
Corresponding author. Mailing address: Department of
Biology, Elizabethtown College, One Alpha Dr., PA 17022-2298. Phone: (717) 361-1448. Fax: (717) 361-1176. E-mail:
cavender{at}acad.etown.edu.
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