Morphological transformation of human adenoviruses is determined to a large extent by gene products of region E1a.

The role of region E1a and E1b of human adenovirus (Ad) types 5 and 12 in determining the morphology of transformed colonies has been studied. Primary baby rat kidney cells were transfected with a mixture of plasmids containing Ad5 region E1a and Ad12 region E1b, or vice versa, and the morphology of the resulting transformed colonies was studied. It was found that the morphology of the colonies was correlated with the identity of the E1a region present in the cells; i.

Expression of region E1b of human adenoviruses in the absence of region E1a is not sufficient for complete transformation.

Previous work has suggested that morphological transformation of cultured cells by human adenoviruses of subgroups A, B, and C is predominantly a function of early region 1b (E1b), and that region E1a has a role in immortalization. To test the hypothesis that region E1b is essentially responsible for the induction of the transformed phenotype the transforming activity of region E1b in the absence of region E1a was reinvestigated. In agreement with previous results, region E1b had no detectable transforming activity in primary baby rat kidney (BRK) cells nor in established rat cell lines.

Analysis of virus-specific mRNAs present in cells transformed with restriction fragments of adenovirus type 5 DNA.

Adenovirus type 5 (Ad5) mRNAs present in cells transformed with left-terminal Ad5 DNA fragments (XhoI-C, 0 to 15.5%; HindIII-G, 0 to 7.7%; HpaI-E, 0 to 4.

The relationship between region E1a and E1b of human adenoviruses in cell transformation.

Baby rat kidney (BRK) cells were transfected either with intact region E1 DNA of adenovirus type 5 (Ad5) or with mixtures of DNA fragments containing the separated E1a and E1b regions. The results showed that mixtures of regions E1a and E1b transform with a similar efficiency as intact region E1. DNA fragments containing region E1b alone have no detectable transforming activity in primary BRK cells nor in established rat cell lines.

The 2.2 kb E1b mRNA of human Ad12 and Ad5 codes for two tumor antigens starting at different AUG triplets.

By nucleotide sequence analysis and S1 nuclease mapping we have determined the structural organization of early region E1b of Ad12. We have also revised the nucleotide sequence of the E1b region of Ad5. Both regions have an identical structural organization and show considerable homology at the nucleotide level.

Binding of labeled initiation factor IF-1 to ribosomal particles and the relationship to the mode of IF-1 action in ribosome dissociation.

The binding of labeled initiation factor IF-1 to ribosomal particles has been studied in relation to the mode of action of this factor in the dissociation of 70-S ribosomes. It is demonstrated that IF-1 interacts specifically with active 70-S tight couples and free 30-S subunits. The binding of IF-1 to both 70-S and 30-S particles is not influenced by the Mg2+ concentration and the affinity of the factor for both particles is about the same.

Induced mutagenesis in dam- mutants of Escherichia coli: a role for 6-methyladenine residues in mutation avoidance.

E. coli strains carrying the dam-3 and dam-4 mutations resulting in reduced levels of 6-methyladenine in the DNA have been found to be more sensitive to base analogue mutagenesis than dam+ strains. Mutagenesis by EMS was also found to be enhanced in dam- strains.

[Methods for population sampling of the immature stages of Simulium damnosum Theobald, 1903 (Diptera, Simuliidae) in West Africa. I. Preliminary observations on the vertical distribution of larvae and pupae (author's transl)].

Three techniques for sampling larvae of Simulium damnosum in different water depths are described. Preliminary results prove that the larvae can settle much deeper, i.e.

Cooperative effects of initiation factors and fMet-tRNA in the formation of the 40-S initiation complex.

In this paper the mode of action of IF-1 in 40-S initiation complex formation was studied with MS2 RNA as messenger. Using initiation factors IF-2 and IF-3 labeled in vitro it appeared that IF-1 did not influence the binding of these factors in the absence of fMet-tRNA. However, in the presence of fMet-tRNA it was found that the enhancement of the fMet-tRNA binding by IF-1 was accompanied with an equimolar increase in binding of IF-2.