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Clonal cell lines derived from cultures infected with a polytropic MuLV release vastly different levels of infectious virions ranging from undetectable to very high. Low producing clones release an overwhelming proportion of non-infectious virions containing retroviral RNA but deficient in the Env protein. Non-infectious virion production is not due to an inability of the cells to support infectious...
We have demonstrated in a mouse model that infection with a retrovirus can lead not only to the generation of recombinants between exogenous and endogenous gammaretrovirus, but also to the mobilization of endogenous proviruses by pseudotyping entire polytropic proviral transcripts and facilitating their infectious spread to new cells. However, the frequency of this occurrence, the kinetics, and the...
The vaccinia virus I3L gene encodes a single-stranded DNA binding protein (SSB) that is essential for virus DNA replication and is conserved in all Chordopoxviruses. The I3 protein contains a negatively charged C-terminal tail that is a common feature of SSBs. Such acidic tails are critical for SSB-dependent replication, recombination and repair. We cloned and purified variants of the I3 protein,...
Currently, little is known about the ankyrin/F-box protein B4. Here, we report that B4R-null viruses exhibited reduced plaque size in tissue culture, and decreased ability to spread, as assessed by multiple-step growth analysis. Electron microscopy indicated that B4R-null viruses still formed mature and extracellular virions; however, there was a slight decrease of virions released into the media...
Vaccinia virus (VACV) strain TianTan was used for much of China's modern history to vaccinate against smallpox, however the only genome sequence contains errors. We have sequenced additional examples of TianTan to obtain a better picture of this important virus. We detected two different subclones. One (TP03) encodes large deletions in the terminal repeats that extend into both VEGF genes and create...
Proinflammatory cytokines and chemokines are often detected in brain tissue of patients with neurological diseases such as multiple sclerosis (MS), HIV-associated dementia (HAD) and Alzheimer's disease (AD). We have utilized a mouse model of retrovirus-induced neurological disease to examine how these proinflammatory responses contribute to neuropathogenesis. In previous studies with this model, a...
Shope fibroma virus and myxoma virus encode proteins predicted to be Type II photolyases. These are enzymes that catalyze light-dependent repair of cyclobutane pyrimidine dimers (CPDs). When the Shope fibroma virus S127L gene was expressed in an Escherichia coli strain lacking functional CPD repair pathways, the expressed gene protected the bacteria from 70-75% of the ultraviolet (UV) light-induced...
Poxviruses appear to use single-strand annealing reactions to recombine linear molecules sharing short (<20 bp) regions of end homology. We have examined the effect of base mismatches and base insertions on the reaction efficiency and used mismatch-containing DNAs to further characterize the polarity of the exonuclease postulated to catalyze these reactions in vivo. Incorporating one or two base...
Vertebrate poxviruses encode homologs of cellular cupro-zinc superoxide dismutases (Cu-Zn SOD). In this study we have examined the molecular genetic properties of two Cu-Zn SOD homologs encoded by the Shope fibroma virus (SFV) and myxoma virus. These Leporipoxvirus proteins should be catalytically inactive as judged by the point mutations which alter a key catalytic arginine and restructure the predicted...
During poxvirus infection, both viral genomes and transfected DNAs are converted into high-molecular-weight concatemers by the replicative machinery. However, aside from the fact that concatemer formation coincides with viral replication, the mechanism and protein(s) catalyzing the reaction are unknown. Here we show that vaccinia virus DNA polymerase can catalyze single-stranded annealing reactions...
We have determined the complete DNA sequence of the Leporipoxvirus Shope fibroma virus (SFV). The SFV genome spans 159.8 kb and encodes 165 putative genes of which 13 are duplicated in the 12.4-kb terminal inverted repeats. Although most SFV genes have homologs encoded by other Chordopoxvirinae, the SFV genome lacks a key gene required for the production of extracellular enveloped virus. SFV also...
Vaccinia virus infection results in the synthesis of a protein that promotes joint molecule formation and strand-transfer reactionsin vitro. We show here that this activity is also expressed by vaccinia DNA polymerase (gpE9L). Recombinant vaccinia polymerase was produced using a hybrid vaccinia/T7 expression system and purified to homogeneity. This protein catalyzed joint molecule formation and strand...
Poxviral DNA topoisomerases are sequence-specific enzymes whose activities are thought to influence such diverse processes as transcription, DNA replication, and genetic recombination. To obtain further insights into the relatedness of these enzymes, and their influence on virus-mediated recombination, we have determined the target-specificity and other catalytic properties of the Shope fibroma virus...
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