Frog Virus 3 DNA Replication Occurs in Two Stages
TL;DR: Results of pulse-chase experiments showed that the concatemeric DNA served as the precursor for the production of mature FV3 DNA, suggesting that this mode of replication is strikingly different from any other known DNA virus.
Abstract: Viral DNA synthesis in frog virus 3 (FV3)-infected cells occurs both in the nucleus and in the cytoplasm (Goorha et al., Virology 84:32-51, 1978). Relationships between viral DNA molecules synthesized in these two compartments and their role in the virus replication were examined. The data presented here suggest that (i) FV3 DNA replicated in two stages and (ii) nucleus and cytoplasm were the sites of stages 1 and 2 of DNA replication, respectively. Stages 1 and 2 were further distinguished by their temporal appearance during infection and by the sizes of the replicating DNA as determined by sedimentation in neutral sucrose gradients. In stage 1, replicating molecules, between the size of unit and twice the unit length, were produced early in infection (2 h postinfection). In contrast, stage 2 of DNA replication occurred only after 3 h postinfection, and replicating molecules were large concatemers. Results of pulse-chase experiments showed that the concatemeric DNA served as the precursor for the production of mature FV3 DNA. Denaturation of concatemeric DNA with alkali or digestion with S1 nuclease reduced it to less than genome size molecules, indicating the presence of extensive single-stranded regions. Analysis of replicating DNA by equilibrium centrifugation in CsCl gradients after a pulse-chase suggested that these single-stranded regions were subsequently repaired. Based on these and previous data, a scheme of FV3 replication is presented. According to this scheme, FV3 utilizes the nucleus for early transcription and stage 1 of DNA replication. The viral DNA is then transported to the cytoplasm, where it participates in stage 2 DNA replication to form a concatemeric replication complex. The processing of concatemers to produce mature viral DNA and virus assembly also occurs in the cytoplasm. This mode of replication is strikingly different from any other known DNA virus.
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TL;DR: The conservation of the disulfide-oxidoreductase, a major capsid protein, and two virion membrane proteins indicates that the odd-shaped virions of poxviruses have evolved from the more common icosahedral virion seen in asfarviruses, iridoviruses, and phycodnaviruses.
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308 citations
Cites background from "Frog Virus 3 DNA Replication Occurs..."
...Following its translation in the cytoplasm, the viral DNA polymerase enters the nucleus where it synthesizes unit to twice unit size copies of the viral genome, representing first stage DNA synthesis (Goorha, 1982; Goorha et al., 1978)....
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...In contrast, fish infected with megalocytiviruses are lethargic, have abnormal coloration of the body, petechia of the gills, and lesions involving the spleen, gills, and digestive tract (Gibson-Kueh et al., 2003; He et al., 2000; Jung et al., 1997)....
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...ADVANCES IN VIRUS RESEARCH, VOL 65...
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TL;DR: The molecular and genetic basis of viral replication, pathogenesis, and immunity are described, and viral ecology is discussed with reference to members from each of the invertebrate and vertebrate genera.
Abstract: Members of the family Iridoviridae infect a diverse array of invertebrate and cold-blooded vertebrate hosts and are currently viewed as emerging pathogens of fish and amphibians. Iridovirid replication is unique and involves both nuclear and cytoplasmic compartments, a circularly permuted, terminally redundant genome that, in the case of vertebrate iridoviruses, is also highly methylated, and the efficient shutoff of host macromolecular synthesis. Although initially neglected largely due to the perceived lack of health, environmental, and economic concerns, members of the genus Ranavirus, and the newly recognized genus Megalocytivirus, are rapidly attracting growing interest due to their involvement in amphibian population declines and their adverse impacts on aquaculture. Herein we describe the molecular and genetic basis of viral replication, pathogenesis, and immunity, and discuss viral ecology with reference to members from each of the invertebrate and vertebrate genera.
219 citations
Cites background from "Frog Virus 3 DNA Replication Occurs..."
...First-Stage Viral DNA Replication Following synthesis of the viral DNA polymerase and its subsequent translocation into the nucleus, viral DNA replication commences within the nucleus and results in the synthesis of genome-size to twice genome-size DNA molecules (Goorha 1982)....
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...Second-Stage Viral DNA Replication: Concatamer Formation In addition to methylation, viral DNA undergoes a second round of DNA synthesis, which results in the formation of large, concatameric structures that are more than ten times larger than genome-sized units (Goorha 1982)....
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...In addition to methylation, viral DNA undergoes a second round of DNA synthesis, which results in the formation of large, concatameric structures that are more than ten times larger than genome-sized units (Goorha 1982)....
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...Following synthesis of the viral DNA polymerase and its subsequent translocation into the nucleus, viral DNA replication commences within the nucleus and results in the synthesis of genome-size to twice genome-size DNA molecules (Goorha 1982)....
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Book•
01 Oct 1989TL;DR: Viruses of lower vertebrates recently became a field of interest to the public due to increasing epizootics and economic losses of poikilothermic animals and some of the DNA viruses seem to be emerging pathogens involved in the worldwide decline in wildlife.
Abstract: Viruses of lower vertebrates recently became a field of interest to the public due to increasing epizootics and economic losses of poikilothermic animals. These were reported worldwide from both wildlife and collections of aquatic poikilothermic animals. Several RNA and DNA viruses infecting fish, amphibians and reptiles have been studied intensively during the last 20 years. Many of these viruses induce diseases resulting in important economic losses of lower vertebrates, especially in fish aquaculture. In addition, some of the DNA viruses seem to be emerging pathogens involved in the worldwide decline in wildlife. Irido-, herpes- and polyomavirus infections may be involved in the reduction in the numbers of endangered amphibian and reptile species. In this context the knowledge of several important RNA viruses such as orthomyxo-, paramyxo-, rhabdo-, retro-, corona-, calici-, toga-, picorna-, noda-, reo- and birnaviruses, and DNA viruses such as parvo-, irido-, herpes-, adeno-, polyoma- and poxviruses, is described in this review.
215 citations