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J Virol, July 1998, p. 6181-6185, Vol. 72, No. 7
Transgène S.A., 67000 Strasbourg,
France,1 and
Deutsches
Krebsforschungszentrum, Forschungsschwerpunkt Angewandte
Tumorvirologie, 69120 Heidelberg, Germany2
Received 1 December 1997/Accepted 23 March 1998
A 100-fold increase in luciferase activity was observed in 293 cells, stably expressing Epstein-Barr nuclear antigen 1 (EBNA1; 293-EBNA1 cells), that had been transiently transfected with plasmids carrying Epstein-Barr virus (EBV) oriP sequences. This
increase was observed in comparison to reporter gene activity obtained after transfection with a plasmid carrying no oriP
sequences. The luciferase gene on these plasmids was under the control
of either the cytomegalovirus immediate-early 1 gene enhancer-promoter (CMV IE1) or the Rous sarcoma virus promoter. The increase of reporter
gene activity was not due to plasmid replication, since a similar
enhancement was observed in the presence of aphidicolin, an inhibitor
of replicative DNA synthesis, or after deletion of the dyad symmetry
(DS) element within oriP. Luciferase production was not increased in the presence of only the DS element.
Microinjection of plasmids carrying the CMV IE1 promoter-driven
luciferase gene with or without oriP sequences into the
nuclei of 293-EBNA1 cells resulted in a 17-fold increase in luciferase
activity. Cytoplasmic injection of these plasmids led to an enhancement
of luciferase activity of up to 100-fold. This difference in the factor
of activation after nuclear or cytoplasmic injection could be ascribed
to increased transport of plasmids carrying oriP from the
cytoplasm to the nucleus in the presence of EBNA1. These data suggest
the possibility of substantially increasing the apparent expression of
a gene under the control of a strong constitutive promoter in the
presence of oriP sequences and EBNA1. This improvement in
expression is due to intranuclear enhancement of gene expression.
oriP-specific transport of plasmid DNA from the cytoplasm
of 293-EBNA1 cells to the nucleus seems to contribute to the observed
effect.
0022-538X/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Up to 100-Fold Increase of Apparent Gene Expression in the
Presence of Epstein-Barr Virus oriP Sequences and EBNA1:
Implications of the Nuclear Import of Plasmids

*
Corresponding author. Mailing address: Transgène
S.A., 11 rue de Molsheim, 67000 Strasbourg, France. Phone: (33) 3 88 27 91 00. Fax: (33) 3 88 22 58 07. E-mail: rittner{at}transgene.fr.
Present address: Institut für Virologie,
Veterinärmedizinische Universität, 1210 Vienna,
Austria.
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