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J. Virol., Oct 1997, 7421-7428, Vol 71, No. 10
J Nesper, RW Smith, AR Kautz, E Sock, M Wegner, F Grummt and HP Nasheuer
The human polyomavirus JC virus (JCV) establishes persistent infections in
most individuals and is the etiologic agent of progressive multifocal
leukoencephalopathy. In this report, we describe the establishment of a
soluble cell-free system that is capable of replicating exogenous plasmid
DNA containing the JCV origin of replication. Replication in this system is
completely dependent on the addition of JCV large T antigen (TAg). To
prepare JCV TAg for replication analysis, a recombinant baculovirus
containing the JCV TAg- coding sequence was generated. TAg expressed in
insect cells was purified by metal chelate chromatography. JCV TAg
supported initiation of JCV DNA replication in the presence of DNA
polymerase alpha-primase, replication protein A, and topoisomerase I in a
dose-dependent manner and was also capable of supporting DNA replication in
crude human cell extracts. Point mutation of TAg-binding site I strongly
diminished TAg binding and concomitantly reduced JCV DNA replication in
vivo and in vitro by approximately 50%. Point mutation of TAg-binding site
II or deletion of the early palindrome completely abolished replication of
JCV origin-containing plasmid DNA in vivo and in vitro, marking these
sequences as essential components of the JCV core origin. A comparison of
several TAgs showed that simian virus 40 TAg, but not mouse polyomavirus
(PyV) TAg, supported replication of a plasmid containing a JCV origin.
These findings provide evidence that replication in the cell-free system
faithfully mimics JCV DNA replication in vivo. Therefore, it may be a
useful tool for future analysis of interactions between JCV and its host
cell.
Copyright © 1997, American Society for Microbiology
A cell-free replication system for human polyomavirus JC DNA
Abteilung Biochemie, Institut fur Molekulare Biotechnologie, Jena, Germany.
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