title: Adenovirus early function required for protection of viral and cellular DNA.
abstract: 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.
mesh_terms: D000260:Adenoviruses, Human / Q000235:genetics* / Q000378:metabolism; D002460:Cell Line; D004261:DNA Replication; D004273:DNA, Neoplasm / Q000378:metabolism*; D004279:DNA, Viral / Q000096:biosynthesis / Q000378:metabolism*; D004720:Endonucleases / Q000378:metabolism; D005814:Genes, Viral; D006801:Humans; D009062:Mouth Neoplasms; D009154:Mutation; D013696:Temperature; D014764:Viral Proteins / Q000096:biosynthesis
chemical_list: D004273:DNA, Neoplasm; D004279:DNA, Viral; D014764:Viral Proteins; D004720:Endonucleases