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Biomedical subjects

S Ihara

Publications and source records attributed to S Ihara.

At least 127 records · Page 7Linked to original sources
PubMed1979

Morphogenesis of nuclear inclusions and virus capsids in HEL cells infected with temperature-sensitive mutants of human cytomegalovirus.

The morphogenesis of nuclear inclusions and virus capsids in human embryonic lung cells infected with ts mutants of human cytomegalovirus at permissive (34 degrees C) and non-permissive (39 degrees C) temperatures was studied by indirect immunofluorescence (IF) and electron microscopic analyses and compared with the morphogenesis of these structures in wild-type virus infection with or without phosphonoacetate. Mutants tested belonged to five different complementation groups: two groups were DNA- (those unable to synthesize virus DNA at 39 degrees C) and the others were dna+. Based on the previous finding that the electron-dense, reticular nuclear inclusions (EM-NI) observed by the thin-section analysis correspond with nuclear inclusions (IF-NI) detected by the indirect IF staining (i.e. they occupy the same space in the nucleus), the following conclusions were obtained in ts mutant infection at 39 degrees C: (i) the formation of EM-NI, IF-NI and virus capsids requires replication of virus DNA. (II) The formation of EM-NI is not necessarily accompanied by the formation of IF-NI; EM-NI itself is not IF-positive unless it acquires virus-specific late antigens. (iii) The assembly of virus capsids occurs only in those cells in which EM-NI is formed; however, it can occur without the formation of IF-NI. (iv) Virus capsids assembled are not the major antigens responsible for the fluorescence of nuclear inclusions.

Capsid↗
PubMed1979

Induction of pre-early nuclear antigen(s) in HEL cells infected with human cytomegalovirus.

Human cytomegalovirus (HCMV)-specific nuclear antigen could be detected within 1 hr after infection in human embryo lung cells by the anticomplement immunofluorescence (ACIF) test. This antigen has been named the pre-early nuclear antigen (PENA) in this paper. Serum absorption tests suggested that PENA is immunologically different from the early antigen and the major nuclear inclusion antigens detected by the indirect immunofluorescence test before and after viral DNA replication, respectively. PENA-forming ability of the virus corresponded to its plaque forming ability. PENA formation was not affected by phosphonoacetate but was inhibited by the addition of inhibitors of RNA and protein syntheses or by UV-irradiation of infecting virus, suggesting that the formation of PENA depends on the expression of infecting virus gene functions. Virus-specific proteins were isolated by indirect immunoprecipitation from HCMV-infected cells exposed to 35S-methionine. SDS-polyacrylamide gel electrophoresis of the immunoprecipitate showed that at least two species of virus-specific polypeptides with molecular weights o.f 70,000 and 30,000 were synthesized de novo within 3 hr after infection.

Antigens↗
PubMed1976

Dual transcription of the tryptophan operon translocated into the early region of gamma.

The mode of transcription of the trp operon translocated into the early region of bacteriophage lambda was studied. Synthesis of trp mRNA specific for the translocated trp operon in lambdatrp phage was assayed after infecting a bacteria carrying a deletion mutant (trpAE1), which lacks the whole trp operon but retains a trp regulator gene (trpR). To determine trp mRNA from lambdatrp, phage phi80trp was employed as a source of DNA in hybridization assays. trp mRNA synthesis by lambdatrpE-A, which possesses the intact trp operon, was found to be only partially repressed by fully activated trp repressor in strain trpAE1. On the other hand, trp mRNA synthesis by lambdatrpE-A in strain trpAE1 (lambda), lysogenic for lambda and therefore possessing lambda repressor, was completely repressed when the trp repressor was fully activated by the addition of excess tryptophan. trp mRNA synthesis from the trp operon segment in lambdatrpBA, which carries the trpA and trpB genes but does not possess the trp promoter and operator, was not affected at all by trp repressor but was regulated completely by lambda repressor. The possibility was excluded that the trp mRNA whose synthesis is insensitive to trp repressor is anti-messenger originating from the nonsense(r)-strand of the translocated trp operon of lambdatrp. These observations led to the conclusion that transcription of the translocated trp operon in lambdatrpE-A consists of two types; one is initiated at the trp promoter and is controlled by the trp repressor, another is initiated by a lambda promoter (PL of gene N) and is controlled by the lambda repressor.

Chromosome Aberrations↗
PubMed1976

Differential sensitivity to antibiotics of trp mRNA synthesis originating at the trp promoter and the lambda promoter.

Transcription of the Escherichia coli trp operon translocated into the early region of bacteriophage lambda can occur under the control of either of two promoters, the trp promoter on the lambda promoter (OL of N gene). (Imamato, F. and Tani, S. (1972) Nat. New Biol. 240, 172-175 and Ihara S. and Imamoto, F. (1976) Biochim. Biophys. Acta 432, 199-211). Trp mRNA synthesis originating at the trp promoter stopped when translation was blocked by chloramphenicol tetracycline erythromycin or puromycin. In contrast, trp mRNA synthesis originating at the lambda promoter was not affected by antibiotic action. This probably is a reflection of the properties of the "immediate early" class of genes of lambda, whose transcription in initiated at the PL. promoter and is not inhibited by the antibiotic. The inference is strengthened by comparable results with phage lambdatrpE-A (carrying an intact tro operon) and lambdatrpBA (carrying the operator-distal two genes but missing the trp promoter and operator). Thus it seems that either the promoter or other gene(s) located at the beginning of the operon, either at polymerase addition or because of some feature of the transcript, can determine a requirement for "coupling" of RNA polymerase to the translational machinery in vivo.

Chloramphenicol↗