| Summary: | 碩士 === 國立中興大學 === 獸醫學系 === 83 === Pseudorabies disease is an important infectious disease of
swine, and pseudorabies virus is the causative agent. The
pseudorabies virus genome is a linear double-stranded
DNA(about 145kbp).The icosahedral capsid approximately
150-180nm in diameter contains 162 capsomeres ,
sometimes asymmetric material surrounding the capsid
designated as the tegument, and an envelope containing viral
glycoprotein spikes on its surface.The pseudorabies virus
genome consists of two covalently linked components ,
designated as unique L(long) and unique S(short), which
were bracketed by inverted repeat and terminal repeat.The
viral DNA is synthesized by a virus-encoded DNA
polymerase and a rolling circle replicating mechanism
has been proposed. Our research goal is to elucidate the
roles of topoisomerases in the replication and expression of
pseudorabies virus. Both type I and II DNA topoisomerases
have been found in prokaryotes and eukaryotes. They have
important roles in cellular DNA replication and
transcription. In animal viruses, topoisomerases also involve
in the life cycle of viruses containing closed circular DNA(
such as SV 40 virus) as well as viruses possessing
double- stranded linear DNA(such as adenovirus and
herpesviruses). Our results reveal that type I
topoisomerase inhibitor (camptothecin) and type II
topoisomerase inhibitors (VP-16 and ellipticine) could
inhibit the multiplication of pseudorabies virus. The type I
topoisomerase activity is essential for the DNA
synthesis of pseudorabies virus.Our findings also suggest
that both type I and type II topoisomerases are required for
the gene expression of the pseudorabies virus genome.
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