Attenuated expression of interferon-induced protein kinase PKR in a simian cell devoid of type I interferons.

The interferon-induced, double-stranded RNA (dsRNA)-dependent protein kinase PKR plays a key role in interferon-mediated host defense against viral infection, and is implicated in cellular transformation and apoptosis. We have isolated a cDNA of simian PKR encoding a product with 83% amino acid identity to the human homolog and showed that PKR expression is significantly attenuated in the Vero E6 African green monkey kidney cells devoid of type I interferon genes. A variant form of PKR lacking the exon 12 in the kinase domain is produced in these cells, presumably from an alternatively spliced transcript. Unlike wild type PKR, the variant protein named PKR-DE12 is incapable of auto-phosphorylation and phosphorylation of eIF2-a, indicating that the kinase sub-domains III and IV embedded in exon 12 are indispensable for catalytic function. PKR-DE12 had no dominant negative effect but was weakly phosphorylated in trans by wild type PKR.

[Nucleotide sequence of the E1B area and the adjacent 3'-terminal segment of the E1A oncogene from monkey adenovirus SA7 (C8)]. / Nukleotidnaia posledovatel'nost' oblasti E1B i primykaiushchego k nei 3'-kontsevogo uchastka oblasti E1A onkogena adenoviursa obez'ian SA7 (C8).

The SA7 (C8) simian adenovirus was sequenced from the 1478th to 3194th nucleotide. The region includes the 3'-terminal part of E1A and the major part of the E1B coding region. The sequence obtained was compared with the structure of SA7 (P) DNA previously determined in the region 1-2338, and many differences were found which are nucleotide substitutions, microdeletions and microinsertions. Among point substitutions the most frequent was the C-->T transition in CG pairs known as hot spots of mutations. Differences of our sequence from the previously published one was also revealed.

[Structure of integrated oncogens E1A and E1B in a malignant line of rat SH2 fibroblasts, transformed by monkey adenovirus SA7 (C8) DNA]. / Struktura integrirovannykh onkogenov D1A i E1B v zlokachestvennoi linii fibroblastov krysy SH2, transformirovannykh DNK adenovirusa obez'ian SA7 (C8).

In this investigation the primary structure of E1A and E1B regions of SA7 (C8) simian adenovirus integrated in malignant SH2 rat cell line was studied. Southern blotting revealed at least two copies of the SA7 oncogene integrated in the SH2 genome. PCR analysis of E1A and E1B regions showed heteroduplex structures, proving the different structure of the integrated copies. The heteroduplex molecules with different electrophoretic mobility were separated, and chains corresponding to different copies were sequenced according to the modified Sanger method. We found that two copies differ mainly in microsatellite regions, in E1A between positions 894-902 (GCG)3/(GCG)4, in E1B between positions 2037-2048 (GCA)3/(GCA)4. It is necessary to stress that all deviations found belong to the coding regions of the SA7 oncogene.

Binding-incompetent adenovirus facilitates molecular conjugate-mediated gene transfer by the receptor-mediated endocytosis pathway.

Molecular conjugate vectors may be constructed that accomplish high efficiency gene transfer by the receptor-mediated endocytosis pathway. In order to mediate escape from lysosomal degradation, we have incorporated adenoviruses into the functional design of the conjugate. In doing so, however, we have introduced an additional ligand, which can bind to receptors on the cell surface, undermining the potential for cell specific targeting. To overcome this, we have treated the adenovirus with a monoclonal anti-fiber antibody, which renders the virus incapable of binding to its receptor. The result is a multi-functional molecular conjugate vector, which has preserved its binding specificity while at the same time being capable of preventing lysosomal degradation of endosome-internalized conjugate-DNA complexes. This finding indicates that adenoviral binding is not a prerequisite for adenoviral-mediated endosome disruption.

[Preparation of single-stranded E1A-oncogene DNA fragments from simian adenovirus SA7 by endonuclease hydrolysis recombinant phage M13 SS-DNA complexed with oligonucleotides, containing restriction sites]. / Poluchenie odnotiazhevykh fragmentov DNK E1A-onkogena adenovirusa obez'ian SA7 gidrolizom éndonukleazami SS-DNK rekombinantnykh fagov M13 v kompleksakh s oligonukleotidami, soderzhashchimi saity restriktsii.

The ss-DNA of the (+) and (-) chains of Ela DNA fragment was obtained by hydrolysis of the recombinant bacteriophages M13 mp8G and mp9G (where G is 1-1750 bp:, E1a region of oncogene SA7) in complexes with the 16 bp oligonucleotides containing AluI and BspRI sites of restriction and sequences complementary to E1a SA7. The obtained fragments overlap the E1a zones associated with the immortalizing potential of SA7.

Modification of steroidogenesis in a mouse adrenal cell line (Y-1) transformed by simian adenovirus SA-7.

Transformation of a steroidogenic mouse adrenal cell line (Y-1) by simian adenovirus SA7 produced a cell line with low apparent steroidogenic activity. The effect of ACTH and cholera toxin on cyclic AMP production was similar in both not transformed and virus-transformed cells and activity of cyclic AMP-dependent protein kinase was also similar in both cells. In transformed cells, cholesterol was metabolized to delta 5-3 beta-hydroxysteroids, mainly 20 alpha-dihydropregnenolone while in not transformed cells, the major metabolites were delta 4-3 ketosteroids (20 alpha-dihydro- and 11 beta-hydroxy-20 alpha-dihydroprogesterone). In both cell lines ACTH increased the metabolism of cholesterol. Further studies with labelled pregnenolone and progesterone revealed a loss of delta 5-3 beta-hydroxysteroid dehydrogenase/isomerase and 11 beta-hydroxylase activity in the transformed cells.

Sequence of inverted terminal repetitions from different adenoviruses: demonstration of conserved sequences and homology between SA7 termini and SV40 DNA.

We have established the nucleotide sequence for the inverted terminal repetition of human adenovirus type 3, a subgroup B adenovirus. The repetition, which is 136 bp long, shows a high degree of homology with the known sequence for the inverted repetition of adenovirus type 5 (Steenbergh et al., 1977) a subgroup C adenovirus. Partial sequence information convering 120 bp of the inverted terminal repetitions of human serotype 12, a subgroup A member, and of simian adenovirus type 7 has also been obtained. A comparison of the established sequences shows that the terminal repetitions, in particular the first 50 bp from the ends, contain sequences that have been well conserved in adenovirus evolution. For instance, only six mismatched base pairs were detected among the first 50 bp in the repetitions of simian adenovirus type 7 and human adenovirus type 5, although the homology between simian adenovirus 7 and human subgroup C adenoviruses was estimated to be only 30%. A 14 bp sequence located 9-22 nucleotides from the ends is present in DNAs from all the human serotypes examined as well as in simian adenovirus 7 DNA. Furthermore, the simian adenovirus 7 repetition contains a 21 bp sequence which is present in SV40 DNA, close to the origin of DNA replication.

Biological activity of the intact and cleaved DNA of the simian adenovirus 7.

Only the deproteinized DNA preparations of the simian adenovirus of the type 7 (SA 7) exhibited transforming and tumorigenic activity. The complex of the SA7 DNA with terminal protein (TP) did not exhibit either transforming or tumorigenic activity in cell cultures. In contrast to the transforming potential the infectious titers of the DNA - TP complex for the monkey kidney cells were 30-50 times higher than those of pure DNA. Cleavage of the SA7 DNA by specific endonucleases enhanced the tumorigenic potential of pure DNA, suppressed its infectivity and did not affect the lack of transformation capacity of the DNA - TP complex. The onc-gene was localized in the left terminal fragment with the minimal size 4,3x10(6)D in the case of R.Sal I. The tumorigenic activity was found to decrease with an increase in the size of the DNA fragment containing the onc-gene.

Late transcription and simultaneous replication of simian adenovirus 7 DNA as revealed by spreading lytically infected cell cultures.

Miller's technique of spreading DNA was applied to monkey cells productively infected with simian adenovirus 7. This permitted the visualization of cellular DNA transcription, both nucleolar and non-nucleolar, and of late transcription and replication of virus. Virus double-stranded DNA, thin fibres with very few nucleosome-like particles, were observed carrying either transcription or replication complexes. In addition, both RNP transcripts and replication forks were found on some virus duplex DNA. Virus single-stranded DNA replicative intermediates were identified on the basis of their increased thickness and contrast which results from the presence of a DNA binding protein.

Localization of simian adenovirus 7 (SA 7) transcription and replication in lytic infection. An ultracytochemical and autoradiographical study.

We have studied SA7 (simian adenovirus 7) lytic infection at the ultrastruct level. The use of cytochemical techniques which specifically stain DNA or preferentially stain ribonucleoproteins permitted the analysis of the structure of the virus-induced nuclear inclusions, and revealed presumed virus DNA before the appearance of other nuclear alterations. Correlation of these findings with high resolution autoradiography enabled the functions of virus DNA replication and transcription to be ascribed to a defined nuclear inclusion. We demonstrate that the nucleolus remains distinct from the inclusion body, contrary to the situation in other adenovirus-infected cells. The functional role of host cell chromatin and of the nucleolus are discussed.