Isolation and characterization of temperature-sensitive mutants of adenovirus type2

Isolation and characterization of temperature-sensitive mutants of adenovirus type 7

Fifty temperature-sensitive mutants, which replicate at 32 degrees C but not at 39.5 degrees C, were isolated after mutagenesis of the vaccine strain of adenovirus type 7 with hydroxylamine (mutation frequency of 9.0%) or nitrous acid (mutation frequency of 3.8%). Intratypic complementation analyses separated 46 of these mutants into seven groups. Intertypic complementation tests with temperature-sensitive mutants of adenovirus type 5 showed that the mutant in complementation group A failed to complement H5ts125 (a DNA-binding protein mutant), that mutants in group B and C did not complement adenovirus type 5 hexon mutants, and that none of the mutants was defective in fiber production. Further phenotypic characterization showed that at the nonpermissive temperature the mutant in group A failed to make immunologically reactive DNA-binding protein, mutants in groups B and C were defective in transport of trimeric hexons to the nucleus, mutants in groups D, E, and F assembled empty capsids, and mutants in group G assembled DNA-containing capsids as well as empty capsids. The mutants of the complementation groups were physically mapped by marker rescue, and the mutations were localized between the following map coordinates: groups B and C between 50.4 and 60.2 map units (m.u.), groups D and E between 29.6 and 36.7 m.u., and group G between 36.7 and 42.0 m.u. or 44.0 and 47.0 m.u. The mutant in group A proved to be a double mutant.

Morphogenesis of human adenovirus type 2 studied with fiber- and fiber and penton base-defective temperature-sensitive mutants

The nature, polypeptide composition, and antigenic composition of the particles formed by six human adenovirus type 2 temperature-sensitive (ts) mutants were studied. ts115, ts116, and ts125 were phenotypically fiber-defective mutants, and ts103, ts104, and ts136 failed to synthesize detectable amounts of fiber plus penton base at 39.5 degrees C. The mutants belonged to five complementation groups, one group including ts116 and ts125. Except for ts103 and ts136, the other mutants were capable of producing particles at 39.5 degrees C. ts116 and ts125 accumulated light assembly intermediate particles (or top components) at nonpermissive temperatures, with few virus particles. The sodium dodecyl sulfate polypeptide pattern of ts116- or ts125-infected cells, intermediate particles, and virus particles showed that polypeptide IV (fiber) was smaller by a molecular weight of 2,000 than that in the wild-type virion and was glycosylated. In fiber plus penton base-defective ts104-infected cells, equivalent quantities of top components and viruses with a buoyant density (rho) of 1.345 g/ml (rho = 1.345 particles) were produced at 39.5 degrees C. These rho = 1.345 particles corresponded to young virions, as evidenced by the presence of uncleaved precursors to proteins VI, VIII, and VII. These young virions matured upon a shift down. Virus capsid vertex antigenic components underwent a phase of eclipse during their incorporation into mature virus particles. No antigenic penton base or IIa was detected in intermediate particles of all the ts mutants tested. Only hexon and traces of fiber antigens were found in ts104 young virions. Penton base and IIIa appeared as fully antigenically expressed capsid subunits in mature wild-type virions or ts104 virions after a shift down. The ts104 lesion is postulated to affect a regulatory function related in some way to penton base and fiber overproduction and the maturation processing of precursors PVI, PVII, and PVII.

Adenovirus early function required for protection of viral and cellular DNA

Studies were done to characterize a DNA-negative temperature-sensitive (ts) mutant of human adenovirus type 2, H2 ts111. The temperature-sensitive defect, which was reversible on shift-down in the absence of protein synthesis, was expressed as early as 2 h postinfection, and the results of density-labeling experiments are in agreement with at least a DNA replication initiation block. On shift-up, after allowing viral DNA synthesis at permissive temperatures, the newly synthesized viral DNA and the mature viral DNA were cleaved into fragments which sedimented as a broad peak with a mean coefficient of 10-12S. This cleavage was more marked in the presence of hydroxyurea as the DNA synthesis inhibitor. Parental DNA in infected cells was degraded to a much lesser extent regardless of the incubation temperature. In contrast, the parental DNA was strongly degraded when early gene expression was permitted at 33 degrees C before shift-up to 39.5 degrees C. Furthermore, cellular DNA was also degraded at 39.5 degrees C in ts111-infected cells, the rate of cleavage being related to the multiplicity of infection. This cleavage effect, which did not seem to be related to penton base-associated endonuclease activity, was also enhanced when early gene expression was allowed at 33 degrees C before shift-up. The ts111 defect, which was related to an initiation block and endonucleolytic cleavage of viral and cellular DNA, seemed to correspond to a single mutation. The implication of the ts111 gene product in protection of viral and cellular DNA by way of a DNase-inhibitory function is discussed.

Interference with simian virus 40 DNA replication by adenovirus type 2 during mixed infection of monkey cells

Infection of monkey cells with human adenovirus (Ad) is abortive, but the infection can be enhanced by coinfecting with simian virus 40 (SV40). However, in the coinfected monkey cells, Ad interferes strongly with SV40 DNA biosynthesis. This interference was found to be a reproducible, delicately controlled phenomenon that was proportional to the multiplicity of infection of Ad and dependent on the active expression of the Ad genome. Newly synthesized SV40 DNA was not broken down in cells after delayed superinfection with Ad, and several early events of SV40 infection such as adsorption, penetration, uncoating, induction of cellular DNA synthesis, and enhancement of Ad infection were not markedly influenced by Ad-mediated interference. It is unlikely that interference is simply due to competition between SV40 and Ad for metabolites, enzymes, or replication sites. The interference effect could be partially neutralized by an increase in the multiplicity of coinfecting SV40 or by an increase in the time interval between SV40 infection and Ad coinfection. Interference was shown to be due to the activity of an Ad early gene product. However, the detailed mechanism of this Ad interference is still unclear.