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J Virol, January 1998, p. 609-616, Vol. 72, No. 1
Institut für Medizinische Mikrobiologie
und Hygiene, Universität Regensburg, D-93053 Regensburg,
Germany,1 and
Service de Microbiologie,
Unité de Virologie, Hopital Saint-Louis and CNRS UPR9051,
F-75010 Paris, France2
Received 9 June 1997/Accepted 1 October 1997
Parvovirus B19 infections are associated with diverse clinical
manifestations, ranging from no symptoms to severe symptoms. The virus
shows an extreme tropism for replication in erythroid progenitor cells,
possibly due to the activity of the only functional promoter (p6) of
the B19 virus genome in combination with both cell- and cell
cycle-specific factors and the trans-activator protein NS1.
As presented here, p6 promoter sequences derived from several B19 virus
isolates proved to be highly conserved. Furthermore, mutations did not
affect any of the potential binding sites for transcription factors.
One variation of the base at position 223 was identified only in B19
virus isolates derived from patients with persistent infection or
chronic arthritis. To determine promoter activity and to characterize
regulatory elements, sequences spanning the total p6 promoter and
subfragments of them were introduced into a eukaryotic expression
vector upstream of the luciferase gene (from Photinus
pyralis). After transfection into HeLa, CEM, BJAB, and K562
cells, the p6 promoter was found to be highly active. When introduced
into the erythroid cell line K562, p6-controlled transcription exceeded
that of the simian virus 40 promoter-enhancer used as a control by more
than 25-fold. Sequence elements relevant for promoter activity mapped
to the regions from nucleotides (nt) 100 to 190 and 233 to 298. Also, the segment from nt 343 to 400 downstream of the TATA box was important
for transcriptional activity in HeLa and K562 cells. By transfecting
the promoter-luciferase constructs into a HeLa cell line stably
carrying the viral NS1 gene under the control of an inducible promoter,
transcriptional activity mediated by the p6 promoter rose significantly
after induction of NS1 expression. The region from nt 100 to 160 proved
to be essential for NS1-mediated transcriptional activation.
Furthermore, NS1-mediated transactivation was dependent on the presence
of two GC-rich elements arranged in tandem upstream of the TATA box.
These data indicate that NS1-mediated p6 transactivation is dependent
on a multicomponent complex combining NS1 with ATF, NF-
0022-538X/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Characterization of cis-Acting and NS1
Protein-Responsive Elements in the p6 Promoter of Parvovirus
B19

B/c-Rel, and
GC-box binding cellular factors.
*
Corresponding author. Mailing address: Institut
für Medizinische Mikrobiologie und Hygiene, Universität
Regensburg, Franz-Josef-Strauss-Allee 11, D-93053, Regensburg, Germany.
Phone: 49-941-944-6454. Fax: 49-941-944-6402. E-mail:
susanne.modrow{at}klinik.uni-regensburg.de.
Present address: ENI-CHEM, Monterotondo 00015, Italy.
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